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CVE-2026-50269 — aiohttp

Fix: aio-libs/aiohttp@bf88077

CVE-2026-50269 is a CWE-93 vulnerability in aiohttp. A fix is available for aiohttp — see the affected versions and patch details below.

AIOHTTP: CRLF injection in multipart headers

Also known asGHSA-m6qw-4cw2-hm4mPYSEC-2026-2106
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-50269.

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs45th percentile — riskier than 45% of all scored CVEsHighest risk
0.00%0.34%0.69%1.03%0.3%0.5%Jul 26Oct 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected
🐍aiohttp

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.0, attacker-controlled input included into multipart/payload headers can be used to modify a request to inject additional headers or similar. 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. This vulnerability is fixed in 3.14.0.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIaiohttpall versions3.14.0pip install --upgrade 'aiohttp==3.14.0'

Affected Products

1 product · 1 configurations
Application
aiohttpaiohttp
< 3.14.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update aiohttp to 3.14.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-50269 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatLow

This Low impact flaw in aiohttp arises from CRLF injection when applications pass untrusted, attacker-controlled input directly into `MultipartWriter.append(headers=...)` or `Payload.headers`. Exploitation is unlikely in typical Red Hat deployments unless custom applications are specifically configured to include…

Workaround published by Red Hat
Sanitize any user-controlled input before passing it to aiohttp's `MultipartWriter.append(headers=...)` or `Payload.headers` methods. Ensure that CRLF characters (carriage return and line feed) are stripped or rejected from header values.
Source: Red Hat security advisory for CVE-2026-50269 (CC BY 4.0)

Frequently Asked Questions

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.0, attacker-controlled input included into multipart/payload headers can be used to modify a request to inject additional headers or similar. 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. This vulnerability is fixed in 3.14.0.
O3 Security · Impact-Aware SCA

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CVE-2026-50269: aiohttp — Fixed in 3.14.0