CVE-2026-50269: aiohttp CRLF Injection Vulnerability

LOW
Advisory Identifier: GHSA-m6qw-4cw2-hm4m
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CWE-113 CWE-93
Published
Advisory Summary

CVE-2026-50269 is a LOW crlf injection vulnerability (CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')) affecting aiohttp libraries in the PyPI ecosystem. The issue involves crlf injection in multipart headers. Remediation is available by upgrading affected packages to version 3.14.0.

CVE-2026-50269 at a Glance

CVE Identifier CVE-2026-50269
GHSA Identifier GHSA-m6qw-4cw2-hm4m
Severity LOW
CVSS v3.1 Base Score N/A
CWE Classification CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
Affected Product aiohttp
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix CVE-2026-50269

To remediate this vulnerability, upgrade all affected aiohttp dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

aiohttp fixed: 3.14.0 
pip install aiohttp>=3.14.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show aiohttp

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-50269, inspect your installed packages using pip:

pip show aiohttp

Analyze the terminal output to locate any version of aiohttp in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.14.0), your application is affected.

Note: The pip show aiohttp command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting'), where the product receives data from an http agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes cr and lf characters before the data is included in outgoing http headers. In aiohttp, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary Attacker-controlled input included into multipart/payload headers can be used to modify a request to inject additional headers or similar. ### Impact In the unlikely situation that an application is passing user-controlled strings into `MultipartWriter.append(headers=...)` or `Payload.headers`, then an attacker may be able to modify the request to inject headers or change the contents of the request. ### Workaround Sanitise such user input. ----- Patch: https://github.com/aio-libs/aiohttp/commit/bf88077ebb14f4c29924b8e8904cba20c55c28b8

CVE-2026-50269 Affected aiohttp Versions

1 component(s)
Fixed Versions:
3.14.0
Product / Package Ecosystem Affected Versions Fixed Version
aiohttp
pypi/aiohttp
PyPI
< 3.14.0
3.14.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/aio-libs/aiohttp/security/advisories/GHSA-m6qw-4cw2-hm4m
Security Fix Commit FIX COMMIT
https://github.com/aio-libs/aiohttp/commit/bf88077ebb14f4c29924b8e8904cba20c55c28b8
aiohttp Source Repository REPOSITORY
https://github.com/aio-libs/aiohttp

Frequently Asked Questions

What is CVE-2026-50269?
CVE-2026-50269 is a security vulnerability in aiohttp involving CRLF injection in multipart headers under CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting').
Which aiohttp versions are affected?
Affected versions include releases prior to 3.14.0 across affected packages: aiohttp.
What version fixes CVE-2026-50269?
Upgrading to 3.14.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is aiohttp affected?
Yes, aiohttp is affected in releases prior to 3.14.0. Upgrade your dependency to 3.14.0 or later.
What CWE is associated with CVE-2026-50269?
CVE-2026-50269 is classified under CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') (The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers.).
How can I check PyPI dependencies for CVE-2026-50269?
Run the dependency tree command: 'pip show aiohttp'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-m6qw-4cw2-hm4m",
  "modified" : "2026-06-15T20:07:26Z",
  "published" : "2026-06-15T20:07:26Z",
  "aliases" : [ "CVE-2026-50269" ],
  "summary" : "aiohttp: CRLF injection in multipart headers",
  "details" : "### Summary\n\nAttacker-controlled input included into multipart/payload headers can be used to modify a request to inject additional headers or similar.\n\n### Impact\n\nIn the unlikely situation that an application is passing user-controlled strings into `MultipartWriter.append(headers=...)` or `Payload.headers`, then an attacker may be able to modify the request to inject headers or change the contents of the request.\n\n### Workaround\n\nSanitise such user input.\n\n-----\n\nPatch: https://github.com/aio-libs/aiohttp/commit/bf88077ebb14f4c29924b8e8904cba20c55c28b8",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "aiohttp"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.14.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.13.5"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/aio-libs/aiohttp/security/advisories/GHSA-m6qw-4cw2-hm4m"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/aio-libs/aiohttp/commit/bf88077ebb14f4c29924b8e8904cba20c55c28b8"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/aio-libs/aiohttp"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-113", "CWE-93" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-15T20:07:26Z",
    "nvd_published_at" : null
  }
}