{"id":"CVE-2026-43969","summary":"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 onward.","aliases":["EEF-CVE-2026-43969","GHSA-g2wm-735q-3f56"],"modified":"2026-08-20T03:30:14.777532120Z","published":"2026-05-11T18:06:40.667Z","database_specific":{"unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"2.9.0"},{"fixed":"*"},{"introduced":"f017f8a0ecbffd5033d9ab49bf180186f7a523a7"},{"fixed":"*"}]}],"cna_assigner":"EEF","cwe_ids":["CWE-93"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43969.json"},"references":[{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-43969"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://cna.erlef.org/cves/CVE-2026-43969.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43969.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43969"},{"type":"FIX","url":"https://github.com/erlef/cowlib/commit/177953dd51540da11090666c1f007214127a1144"},{"type":"PACKAGE","url":"https://github.com/ninenines/cowlib"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/erlef/cowlib","events":[{"introduced":"0"},{"fixed":"177953dd51540da11090666c1f007214127a1144"}],"database_specific":{"source":"REFERENCES"}}],"versions":["2.16.0","2.15.0","2.14.0","2.13.0","2.12.1","2.12.0","2.11.0","2.10.1","2.10.0","2.9.1","2.9.0","2.8.0","2.7.3","2.7.2","2.7.1","2.7.0","2.6.0","2.5.1","2.5.0","2.4.0","2.3.0","2.2.1","2.2.0","2.1.0","2.0.1","2.0.0","2.0.0-rc.1","2.0.0-pre.1","1.0.1","1.3.0","1.2.0","1.1.0","1.0.0","0.6.2","0.6.1","0.6.0","0.5.1","0.5.0","0.4.0","0.3.0","0.2.0","0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43969.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/ninenines/cowlib","events":[{"introduced":"b34155f725245848dca3a505398e262b1d50f25b"},{"last_affected":"bae6b022af54566f3518a3aa59083b4591d552de"}],"database_specific":{"cpe":"cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"2.9.0"},{"last_affected":"2.16.1"}],"source":"CPE_RANGE"}}],"versions":["2.16.1","2.16.0","2.15.0","2.14.0","2.13.0","2.12.1","2.12.0","2.11.0","2.10.1","2.10.0","2.9.1","2.9.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43969.json"}}],"schema_version":"1.9.0","severity":[{"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"}]}