{"id":"GHSA-g2wm-735q-3f56","summary":"cowlib: Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1","details":"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.\n\ncow_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.\n\nThis issue affects cowlib from 2.9.0.","aliases":["CVE-2026-43969","EEF-CVE-2026-43969"],"modified":"2026-06-08T20:31:01.091008738Z","published":"2026-05-11T21:31:34Z","database_specific":{"cwe_ids":["CWE-93"],"severity":"LOW","github_reviewed":true,"github_reviewed_at":"2026-05-18T17:48:35Z","nvd_published_at":"2026-05-11T19:16:25Z"},"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43969"},{"type":"WEB","url":"https://github.com/erlef/cowlib/commit/177953dd51540da11090666c1f007214127a1144"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-43969.html"},{"type":"PACKAGE","url":"https://github.com/ninenines/cowlib"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-43969"}],"affected":[{"package":{"name":"cowlib","ecosystem":"Hex","purl":"pkg:hex/cowlib"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.9.0"},{"last_affected":"2.16.1"}]}],"versions":["2.10.0","2.10.1","2.11.0","2.12.0","2.12.1","2.13.0","2.14.0","2.15.0","2.16.0","2.16.1","2.9.0","2.9.1"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-g2wm-735q-3f56/GHSA-g2wm-735q-3f56.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N"}]}