# CVE-2026-50269: aio-libs aiohttp CRLF injection in multipart headers

Source: https://junglewise.ai/threats/cve-2026-50269-aio-libs-aiohttp-crlf-injection-in-multipart-headers  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-22. Updated: 2026-06-22  
License: CC BY 4.0 with a link back

CVE-2026-50269 · Severity: medium · CVSS 4 · Published 2026-06-22

AIOHTTP is a popular Python library used by developers to build web servers and clients. A security flaw allows attackers to inject unauthorized information into web requests if the application handles user-provided data incorrectly. This could lead to the modification of request contents or the injection of malicious headers, potentially compromising how the application communicates with other services.

Technologies: [aiohttp (PyPI)](https://junglewise.ai/threats/technologies/aiohttp). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-50269 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-50269 being exploited in the wild.

**How severe is CVE-2026-50269?** Medium severity, with a CVSS score of 4, published 22 June 2026.

**Which products and versions are affected?** aiohttp (PyPI) <= 3.13.5, ECOSYSTEM:introduced=0,fixed=3.14.0.

**Is there a fix for CVE-2026-50269?** Yes. aiohttp (PyPI): upgrade to 3.14.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-50269 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-50269?** Check whether you run aiohttp (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- aiohttp (PyPI): upgrade to 3.14.0 or later

  ```sh
  pip install "aiohttp>=3.14.0"
  ```


## Technical details

A CRLF injection vulnerability exists in aiohttp's handling of multipart and payload headers. The root cause is improper neutralization of carriage return and line feed sequences when user-controlled strings are passed into MultipartWriter.append(headers=...) or Payload.headers. An attacker can exploit this by providing specially crafted input that injects additional HTTP headers or modifies the request body. This is a network-reachable vulnerability that requires the application to be specifically configured to pass unsanitized user input into these header fields. The issue is fixed in version 3.14.0 by rejecting invalid bytes in these components.

## Affected products

- aio-libs aiohttp < 3.14.0

## Identifiers

- CVE-2026-50269
- GHSA-m6qw-4cw2-hm4m
- PYSEC-2026-2106

## Timeline

- 2026-06-04: advisory: GitHub Security Advisory published
- 2026-06-22: disclosed: NVD publication date

## References

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

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