Disclosure summary
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 before 2.21.0.
Source-reported weakness categories
CWE-93
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
NIST National Vulnerability Database · NVD-CVE-2026-43969
Open original source · Updated Oct 09, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
| Vendor | Product / association | Version / bounds |
|---|---|---|
| ninenines | cowlib | * {"versionStartIncluding":"2.9.0","versionEndIncluding":"2.16.1"} |
Original records & references
- NIST NVD record
- CVE Program record
- cna.erlef.org — Vendor Advisory
- github.com — Patch
- github.com
- github.com
- osv.dev — Third Party Advisory
PUBLISHED 2026-05-11T15:16:25-04:00
MODIFIED 2026-10-09T03:17:18-04:00
INGESTED 2026-10-10T20:50:35-04:00