BlackSheep's ClientSession is vulnerable to CRLF injection
Impact
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.
Attack vector: Applications using user input in HTTP client requests (method, URL, headers).
Patches
Users who use the HTTP Client in BlackSheep should upgrade to 2.4.6.
Workarounds
If users handle headers from untrusted parties, they might reject values for header names and values that contain carriage returns.
References
https://owasp.org/www-community/vulnerabilities/CRLF_Injection
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | blacksheep | < 2.4.6 | 2.4.6 |
References
- https://github.com/Neoteroi/BlackSheep/security/advisories/GHSA-6pw3-h7xf-x4gp
- https://nvd.nist.gov/vuln/detail/CVE-2026-22779
- https://github.com/Neoteroi/BlackSheep/commit/bd4ecb9542b5d52442276b5a6907931b90f38d12
- https://github.com/Neoteroi/BlackSheep
- https://github.com/Neoteroi/BlackSheep/releases/tag/v2.4.6
- https://pypi.org/project/blacksheep
- https://github.com/advisories/GHSA-6pw3-h7xf-x4gp
- CVSS 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- Weakness (CWE)
CWE-113, CWE-93- Platform
- Python (PyPI)
- Package
blacksheep- Disclosed
- 14.01.2026
- Updated
- 11.10.2026 13:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-1222 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-6pw3-h7xf-x4gp - CC BY 4.0
Vulnerability history: blacksheep
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
Know which vulnerabilities affect your application
With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.