Vulnerability Description
Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows HTTP request splitting and cookie smuggling via unvalidated cookie name and value fields. cow_cookie:cookie/1 in cowlib builds a client-side Cookie: request header from a list of name-value pairs without validating either field. An attacker who controls the cookie names or values passed to this function can inject ;, ,, CR, LF, or TAB characters into the serialized header. This enables two classes of attack: cookie smuggling within a single header (e.g. injecting "; admin=1" to introduce a phantom cookie that the receiving server treats as authentic) and HTTP request header splitting (injecting CRLF to append arbitrary headers or smuggle a complete second request against a shared upstream proxy). The decoder side (parse_cookie_name/1, parse_cookie_value/1) and setcookie/3 already validate and reject these characters; the encoder alone is missing the check. This issue affects cowlib from 2.9.0.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Ninenines | Cowlib | >= 2.9.0, <= 2.16.1 |
Related Weaknesses (CWE)
References
- https://cna.erlef.org/cves/CVE-2026-43969.htmlVendor Advisory
- https://github.com/erlef/cowlib/commit/177953dd51540da11090666c1f007214127a1144Patch
- https://osv.dev/vulnerability/EEF-CVE-2026-43969Third Party Advisory
FAQ
What is CVE-2026-43969?
CVE-2026-43969 is a vulnerability with a CVSS score of 3.2 (LOW). Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows HTTP request splitting and cookie smuggling via unvalidated cookie name and value fields. cow_coo...
How severe is CVE-2026-43969?
CVE-2026-43969 has been rated LOW with a CVSS base score of 3.2/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-43969?
Check the references section above for vendor advisories and patch information. Affected products include: Ninenines Cowlib.