CVE-2026-59249
Sign-tolerant HTTP/1 chunk-size parser in Mint enables response smuggling against strict intermediaries on pooled connections
Description
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.
INFO
Published Date :
July 16, 2026, 12:18 p.m.
Last Modified :
July 16, 2026, 1:49 p.m.
Remotely Exploit :
Yes !
Source :
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | ||||
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db |
Solution
- Update elixir-mint to a non-vulnerable version.
- Ensure HTTP servers correctly format chunk sizes.
- Validate HTTP request handling logic.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-59249.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-59249 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-59249
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-59249 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-59249 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 16, 2026
Action Type Old Value New Value Added Reference https://github.com/elixir-mint/mint/security/advisories/GHSA-x3x7-96vm-6h2w Added SSVC {'id': 'CVE-2026-59249', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-16T12:37:52.637521Z'} -
New CVE Received by 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Jul. 16, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:2.3:a:elixir-mint:mint:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/elixir-mint/mint', 'vendor': 'elixir-mint', 'modules': ["'Elixir.Mint.HTTP1'"], 'product': 'mint', 'versions': [{'status': 'affected', 'version': '0.1.0', 'lessThan': '1.9.3', 'versionType': 'semver'}], 'packageURL': 'pkg:hex/mint', 'packageName': 'mint', 'programFiles': ['lib/mint/http1.ex'], 'collectionURL': 'https://repo.hex.pm', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.Mint.HTTP1':decode_body/5"}]}, {'cpes': ['cpe:2.3:a:elixir-mint:mint:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/elixir-mint/mint', 'vendor': 'elixir-mint', 'modules': ["'Elixir.Mint.HTTP1'"], 'product': 'mint', 'versions': [{'status': 'affected', 'version': '60089586ec7adc9fddb09f69a2f5919ba9ac7f33', 'lessThan': 'fc7d16538db7e40b56ed489f08683225cb0197fa', 'versionType': 'git'}], 'packageURL': 'pkg:github/elixir-mint/mint', 'packageName': 'elixir-mint/mint', 'programFiles': ['lib/mint/http1.ex'], 'collectionURL': 'https://github.com', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.Mint.HTTP1':decode_body/5"}]}] Added Description 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. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-444 Added Reference https://cna.erlef.org/cves/CVE-2026-59249.html Added Reference https://github.com/elixir-mint/mint/commit/fc7d16538db7e40b56ed489f08683225cb0197fa Added Reference https://github.com/elixir-mint/mint/security/advisories/GHSA-x3x7-96vm-6h2w Added Reference https://osv.dev/vulnerability/EEF-CVE-2026-59249