CVE-2026-82391 (GCVE-0-2026-82391)
Vulnerability from cvelistv5 – Published: 2026-11-10 22:07 – Updated: 2026-11-10 22:07
VLAI
EPSS
VEX
Title
Out-of-bounds write in Zephyr HTTP/2 server static-filesystem handler via corrupted receive-buffer length
Summary
The HTTP/2 front-end of the Zephyr HTTP server aliased connection receive state as a scratch output. In subsys/net/lib/http/http_server_http2.c, handle_http2_static_fs_resource() passed &client->data_len as the file_size out-parameter of http_server_find_file(). client->data_len is the count of unprocessed bytes remaining in the fixed-size per-connection receive buffer client->buffer[CONFIG_HTTP_SERVER_CLIENT_BUFFER_SIZE] (256 bytes by default), an invariant every frame handler and the socket receive path rely on. Serving any static file therefore replaced that bounded value with the file's on-disk size, and nothing resets it afterwards.
The defect is reached by an unauthenticated HTTP/2 GET for any file under the web root, in applications that register a static-filesystem resource (HTTP_RESOURCE_TYPE_STATIC_FS) with CONFIG_FILE_SYSTEM=y; CONFIG_HTTP_SERVER_VERSION_2 is enabled by default and no TLS or credentials are required on this path. Once client->data_len exceeds the buffer size, the frame dispatch loop in subsys/net/lib/http/http_server_core.c keeps parsing past the end of the received data, and the peer controls the bytes at client->cursor, so it can choose which fabricated frame the state machine consumes next by appending bytes after its request.
The inflated length defeats the only guards on the buffer. parse_http_frame_header() and the per-frame handlers read and skip up to a 24-bit frame length beyond the buffer (out-of-bounds read); the compaction memmove(client->buffer, client->cursor, client->data_len) at the end of request handling copies the file-size number of bytes into the 256-byte buffer, overflowing the rest of struct http_client_ctx — including the current_detail/current_stream pointers, the parser_settings function-pointer table and the inactivity_timer work handler — and the adjacent client contexts in static memory; and the subsequent zsock_recv(client->fd, client->buffer + client->data_len, sizeof(client->buffer) - client->data_len, 0) underflows its size argument, writing attacker-supplied data of attacker-chosen length out of bounds.
The impact is remote memory corruption in the server's single address space: at minimum a crash or hang of the device, and plausibly control-data overwrite leading to code execution. The HTTP/1 and HTTP/3 static-filesystem handlers already used a local variable and are unaffected; the fix makes the HTTP/2 handler use a local size_t file_size as well.
Severity
9.1 (Critical)
CWE
- CWE-787 - memory-safety
Assigner
References
2 references
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| zephyrproject | zephyr |
Affected:
4.0.0 , < 4.3.2
(semver)
Affected: 4.4.0 , < 4.5.0 (semver) |
guessed |
{
"containers": {
"cna": {
"affected": [
{
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"packageName": "zephyr",
"product": "zephyr",
"programFiles": [
"subsys/net/lib/http/http_server_http2.c"
],
"programRoutines": [
{
"name": "handle_http2_static_fs_resource"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.3.2",
"status": "affected",
"version": "4.0.0",
"versionType": "semver"
},
{
"lessThan": "4.5.0",
"status": "affected",
"version": "4.4.0",
"versionType": "semver"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "The HTTP/2 front-end of the Zephyr HTTP server aliased connection receive state as a scratch output. In subsys/net/lib/http/http_server_http2.c, handle_http2_static_fs_resource() passed \u0026client-\u003edata_len as the file_size out-parameter of http_server_find_file(). client-\u003edata_len is the count of unprocessed bytes remaining in the fixed-size per-connection receive buffer client-\u003ebuffer[CONFIG_HTTP_SERVER_CLIENT_BUFFER_SIZE] (256 bytes by default), an invariant every frame handler and the socket receive path rely on. Serving any static file therefore replaced that bounded value with the file\u0027s on-disk size, and nothing resets it afterwards.\n\nThe defect is reached by an unauthenticated HTTP/2 GET for any file under the web root, in applications that register a static-filesystem resource (HTTP_RESOURCE_TYPE_STATIC_FS) with CONFIG_FILE_SYSTEM=y; CONFIG_HTTP_SERVER_VERSION_2 is enabled by default and no TLS or credentials are required on this path. Once client-\u003edata_len exceeds the buffer size, the frame dispatch loop in subsys/net/lib/http/http_server_core.c keeps parsing past the end of the received data, and the peer controls the bytes at client-\u003ecursor, so it can choose which fabricated frame the state machine consumes next by appending bytes after its request.\n\nThe inflated length defeats the only guards on the buffer. parse_http_frame_header() and the per-frame handlers read and skip up to a 24-bit frame length beyond the buffer (out-of-bounds read); the compaction memmove(client-\u003ebuffer, client-\u003ecursor, client-\u003edata_len) at the end of request handling copies the file-size number of bytes into the 256-byte buffer, overflowing the rest of struct http_client_ctx \u2014 including the current_detail/current_stream pointers, the parser_settings function-pointer table and the inactivity_timer work handler \u2014 and the adjacent client contexts in static memory; and the subsequent zsock_recv(client-\u003efd, client-\u003ebuffer + client-\u003edata_len, sizeof(client-\u003ebuffer) - client-\u003edata_len, 0) underflows its size argument, writing attacker-supplied data of attacker-chosen length out of bounds.\n\nThe impact is remote memory corruption in the server\u0027s single address space: at minimum a crash or hang of the device, and plausibly control-data overwrite leading to code execution. The HTTP/1 and HTTP/3 static-filesystem handlers already used a local variable and are unaffected; the fix makes the HTTP/2 handler use a local size_t file_size as well."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.1,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
"version": "3.1"
},
"format": "CVSS"
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-787",
"description": "memory-safety",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-11-10T22:07:39.047Z",
"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr"
},
"references": [
{
"name": "Fix commit",
"tags": [
"patch"
],
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/4e0a5f38b14dba5891fb558c49a526f9f6a3cc29"
},
{
"name": "GHSA-8jrg-wx88-g75j",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8jrg-wx88-g75j"
}
],
"title": "Out-of-bounds write in Zephyr HTTP/2 server static-filesystem handler via corrupted receive-buffer length",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"assignerShortName": "zephyr",
"cveId": "CVE-2026-82391",
"datePublished": "2026-11-10T22:07:39.047Z",
"dateReserved": "2026-08-28T21:11:46.166Z",
"dateUpdated": "2026-11-10T22:07:39.047Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"packageName": "zephyr",
"product": "zephyr",
"programFiles": [
"subsys/net/lib/http/http_server_http2.c"
],
"programRoutines": [
{
"name": "handle_http2_static_fs_resource"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.3.2",
"status": "affected",
"version": "4.0.0",
"versionType": "semver"
},
{
"lessThan": "4.5.0",
"status": "affected",
"version": "4.4.0",
"versionType": "semver"
}
]
}
],
"source": "vulnerabilities@zephyrproject.org"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "The HTTP/2 front-end of the Zephyr HTTP server aliased connection receive state as a scratch output. In subsys/net/lib/http/http_server_http2.c, handle_http2_static_fs_resource() passed \u0026client-\u003edata_len as the file_size out-parameter of http_server_find_file(). client-\u003edata_len is the count of unprocessed bytes remaining in the fixed-size per-connection receive buffer client-\u003ebuffer[CONFIG_HTTP_SERVER_CLIENT_BUFFER_SIZE] (256 bytes by default), an invariant every frame handler and the socket receive path rely on. Serving any static file therefore replaced that bounded value with the file\u0027s on-disk size, and nothing resets it afterwards.\n\nThe defect is reached by an unauthenticated HTTP/2 GET for any file under the web root, in applications that register a static-filesystem resource (HTTP_RESOURCE_TYPE_STATIC_FS) with CONFIG_FILE_SYSTEM=y; CONFIG_HTTP_SERVER_VERSION_2 is enabled by default and no TLS or credentials are required on this path. Once client-\u003edata_len exceeds the buffer size, the frame dispatch loop in subsys/net/lib/http/http_server_core.c keeps parsing past the end of the received data, and the peer controls the bytes at client-\u003ecursor, so it can choose which fabricated frame the state machine consumes next by appending bytes after its request.\n\nThe inflated length defeats the only guards on the buffer. parse_http_frame_header() and the per-frame handlers read and skip up to a 24-bit frame length beyond the buffer (out-of-bounds read); the compaction memmove(client-\u003ebuffer, client-\u003ecursor, client-\u003edata_len) at the end of request handling copies the file-size number of bytes into the 256-byte buffer, overflowing the rest of struct http_client_ctx \u2014 including the current_detail/current_stream pointers, the parser_settings function-pointer table and the inactivity_timer work handler \u2014 and the adjacent client contexts in static memory; and the subsequent zsock_recv(client-\u003efd, client-\u003ebuffer + client-\u003edata_len, sizeof(client-\u003ebuffer) - client-\u003edata_len, 0) underflows its size argument, writing attacker-supplied data of attacker-chosen length out of bounds.\n\nThe impact is remote memory corruption in the server\u0027s single address space: at minimum a crash or hang of the device, and plausibly control-data overwrite leading to code execution. The HTTP/1 and HTTP/3 static-filesystem handlers already used a local variable and are unaffected; the fix makes the HTTP/2 handler use a local size_t file_size as well."
}
],
"id": "CVE-2026-82391",
"lastModified": "2026-11-10T22:21:05.823",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.1,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 5.2,
"source": "vulnerabilities@zephyrproject.org",
"type": "Secondary"
}
]
},
"published": "2026-11-10T22:21:05.710",
"references": [
{
"source": "vulnerabilities@zephyrproject.org",
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/4e0a5f38b14dba5891fb558c49a526f9f6a3cc29"
},
{
"source": "vulnerabilities@zephyrproject.org",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8jrg-wx88-g75j"
}
],
"sourceIdentifier": "vulnerabilities@zephyrproject.org",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-787"
}
],
"source": "vulnerabilities@zephyrproject.org",
"type": "Secondary"
}
]
}
}
}
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.