CVE-2026-59249 (GCVE-0-2026-59249)
Vulnerability from cvelistv5 – Published: 2026-07-16 11:39 – Updated: 2026-07-17 10:11
VLAI
EPSS
VEX
Title
Sign-tolerant HTTP/1 chunk-size parser in Mint enables response smuggling against strict intermediaries on pooled connections
Summary
Inconsistent interpretation of HTTP requests (HTTP response smuggling) vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on the same pooled connection, enabling response-queue poisoning against subsequent requests that share the connection.
The Mint.HTTP1.decode_body/5 function in lib/mint/http1.ex parses the chunk-size line of a Transfer-Encoding: chunked response with Integer.parse(data, 16). RFC 7230 defines chunk-size = 1*HEXDIG and forbids any sign prefix, but Integer.parse/2 accepts an optional leading + or -. A chunk-size line of +5 is accepted as a five-byte chunk; lines of +0 and -0 are accepted as the terminating zero-length chunk and end the message body early.
An RFC-strict intermediary in the response path rejects these forms, so the intermediary and the Mint client disagree on where one response ends and the next begins. On a pooled keep-alive connection, an attacker-influenced origin can inject bytes that the client attributes to the next legitimate response on the same connection, poisoning the response queue and corrupting the responses returned to unrelated in-flight requests.
This issue affects mint: from 0.1.0 before 1.9.3.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-16 12:37 UTC
CWE
- CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/elixir-mint/mint/security/advi… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-59249.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-59249 | related |
| https://github.com/elixir-mint/mint/commit/fc7d16… | patch |
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| elixir-mint | mint |
Affected:
0.1.0 , < 1.9.3
(semver)
cpe:2.3:a:elixir-mint:mint:*:*:*:*:*:*:*:* |
||
| elixir-mint | mint |
Affected:
60089586ec7adc9fddb09f69a2f5919ba9ac7f33 , < fc7d16538db7e40b56ed489f08683225cb0197fa
(git)
cpe:2.3:a:elixir-mint:mint:*:*:*:*:*:*:*:* |
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"lessThan": "1.9.3",
"status": "affected",
"version": "0.1.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:elixir-mint:mint:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Mint.HTTP1\u0027"
],
"packageName": "elixir-mint/mint",
"packageURL": "pkg:github/elixir-mint/mint",
"product": "mint",
"programFiles": [
"lib/mint/http1.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Mint.HTTP1\u0027:decode_body/5"
}
],
"repo": "https://github.com/elixir-mint/mint",
"vendor": "elixir-mint",
"versions": [
{
"lessThan": "fc7d16538db7e40b56ed489f08683225cb0197fa",
"status": "affected",
"version": "60089586ec7adc9fddb09f69a2f5919ba9ac7f33",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eExploitation requires a deployment topology in which an RFC-strict HTTP/1 intermediary (proxy, load balancer, or WAF) sits between the Mint client and the attacker-influenced origin, and HTTP/1 connections between the client and the intermediary are reused across requests (keep-alive with connection pooling). Mint clients that talk directly to an origin without an intermediary, or that do not reuse connections, are not exploitable for response-queue poisoning even if the vulnerable parsing behavior is present.\u003c/p\u003e"
}
],
"value": "Exploitation requires a deployment topology in which an RFC-strict HTTP/1 intermediary (proxy, load balancer, or WAF) sits between the Mint client and the attacker-influenced origin, and HTTP/1 connections between the client and the intermediary are reused across requests (keep-alive with connection pooling). Mint clients that talk directly to an origin without an intermediary, or that do not reuse connections, are not exploitable for response-queue poisoning even if the vulnerable parsing behavior is present."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:elixir-mint:mint:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.9.3",
"versionStartIncluding": "0.1.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Thepigtails"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Andrea Leopardi"
},
{
"lang": "en",
"type": "remediation reviewer",
"value": "Eric Meadows-J\u00f6nsson"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen / EEF"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eInconsistent interpretation of HTTP requests (HTTP response smuggling) vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on the same pooled connection, enabling response-queue poisoning against subsequent requests that share the connection.\u003c/p\u003e\u003cp\u003eThe \u003ctt\u003eMint.HTTP1.decode_body/5\u003c/tt\u003e function in \u003ctt\u003elib/mint/http1.ex\u003c/tt\u003e parses the chunk-size line of a \u003ctt\u003eTransfer-Encoding: chunked\u003c/tt\u003e response with \u003ctt\u003eInteger.parse(data, 16)\u003c/tt\u003e. RFC 7230 defines \u003ctt\u003echunk-size = 1*HEXDIG\u003c/tt\u003e and forbids any sign prefix, but \u003ctt\u003eInteger.parse/2\u003c/tt\u003e accepts an optional leading \u003ctt\u003e+\u003c/tt\u003e or \u003ctt\u003e-\u003c/tt\u003e. A chunk-size line of \u003ctt\u003e+5\u003c/tt\u003e is accepted as a five-byte chunk; lines of \u003ctt\u003e+0\u003c/tt\u003e and \u003ctt\u003e-0\u003c/tt\u003e are accepted as the terminating zero-length chunk and end the message body early.\u003c/p\u003e\u003cp\u003eAn RFC-strict intermediary in the response path rejects these forms, so the intermediary and the Mint client disagree on where one response ends and the next begins. On a pooled keep-alive connection, an attacker-influenced origin can inject bytes that the client attributes to the next legitimate response on the same connection, poisoning the response queue and corrupting the responses returned to unrelated in-flight requests.\u003c/p\u003e\u003cp\u003eThis issue affects mint: from 0.1.0 before 1.9.3.\u003c/p\u003e"
}
],
"value": "Inconsistent interpretation of HTTP requests (HTTP response smuggling) vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on the same pooled connection, enabling response-queue poisoning against subsequent requests that share the connection.\n\nThe Mint.HTTP1.decode_body/5 function in lib/mint/http1.ex parses the chunk-size line of a Transfer-Encoding: chunked response with Integer.parse(data, 16). RFC 7230 defines chunk-size = 1*HEXDIG and forbids any sign prefix, but Integer.parse/2 accepts an optional leading + or -. A chunk-size line of +5 is accepted as a five-byte chunk; lines of +0 and -0 are accepted as the terminating zero-length chunk and end the message body early.\n\nAn RFC-strict intermediary in the response path rejects these forms, so the intermediary and the Mint client disagree on where one response ends and the next begins. On a pooled keep-alive connection, an attacker-influenced origin can inject bytes that the client attributes to the next legitimate response on the same connection, poisoning the response queue and corrupting the responses returned to unrelated in-flight requests.\n\nThis issue affects mint: from 0.1.0 before 1.9.3."
}
],
"impacts": [
{
"capecId": "CAPEC-273",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-273 HTTP Response Smuggling"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 6.3,
"baseSeverity": "MEDIUM",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "LOW",
"vulnIntegrityImpact": "LOW"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-444",
"description": "CWE-444 Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-07-17T10:11:36.783Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/elixir-mint/mint/security/advisories/GHSA-x3x7-96vm-6h2w"
},
{
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-59249.html"
},
{
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-59249"
},
{
"tags": [
"patch"
],
"url": "https://github.com/elixir-mint/mint/commit/fc7d16538db7e40b56ed489f08683225cb0197fa"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Sign-tolerant HTTP/1 chunk-size parser in Mint enables response smuggling against strict intermediaries on pooled connections",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-59249",
"datePublished": "2026-07-16T11:39:29.939Z",
"dateReserved": "2026-07-04T04:24:03.652Z",
"dateUpdated": "2026-07-17T10:11:36.783Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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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
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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.
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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.