CVE-2026-22779 — blacksheep
Fix: Neoteroi/BlackSheep@bd4ecb9CVE-2026-22779 is a CWE-113 vulnerability in blacksheep. A fix is available for blacksheep — see the affected versions and patch details below.
BlackSheep ClientSession is vulnerable to CRLF injection
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-2026-22779.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
blacksheepReal-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
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | blacksheep | all versions | 2.4.6pip install --upgrade 'blacksheep==2.4.6' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for blacksheep, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update blacksheep to 2.4.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-22779 is resolved across your whole dependency graph.
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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-22779 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-22779. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-22779 in your dependencies?
O3 Security finds CVE-2026-22779 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.