{"id":"CVE-2026-43969","revision":"c0226393cc10445b8ca9c371920f7d94","records":[{"revision":"c0226393cc10445b8ca9c371920f7d94","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-43969","aliases":[],"title":"Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1","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.\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 before 2.21.0.","state":0,"publishedAt":"2026-05-11T18:06:40.667+00:00","modifiedAt":"2026-10-09T06:57:15.234+00:00","affected":[{"ecosystem":"https://repo.hex.pm","name":"cowlib","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"collectionURL\": \"https://repo.hex.pm\",\n                    \"cpes\": [\n                        \"cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*\"\n                    ],\n                    \"defaultStatus\": \"unaffected\",\n                    \"modules\": [\n                        \"cow_cookie\"\n                    ],\n                    \"packageName\": \"cowlib\",\n                    \"packageURL\": \"pkg:hex/cowlib\",\n                    \"product\": \"cowlib\",\n                    \"programFiles\": [\n                        \"src/cow_cookie.erl\"\n                    ],\n                    \"programRoutines\": [\n                        {\n                            \"name\": \"cow_cookie:cookie/1\"\n                        }\n                    ],\n                    \"repo\": \"https://github.com/ninenines/cowlib\",\n                    \"vendor\": \"ninenines\",\n                    \"versions\": [\n                        {\n                            \"lessThan\": \"2.21.0\",\n                            \"status\": \"affected\",\n                            \"version\": \"2.9.0\",\n                            \"versionType\": \"semver\"\n                        }\n                    ]\n                }"},{"ecosystem":"https://github.com","name":"ninenines/cowlib","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"collectionURL\": \"https://github.com\",\n                    \"cpes\": [\n                        \"cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*\"\n                    ],\n                    \"defaultStatus\": \"unaffected\",\n                    \"modules\": [\n                        \"cow_cookie\"\n                    ],\n                    \"packageName\": \"ninenines/cowlib\",\n                    \"packageURL\": \"pkg:github/ninenines/cowlib\",\n                    \"product\": \"cowlib\",\n                    \"programFiles\": [\n                        \"src/cow_cookie.erl\"\n                    ],\n                    \"programRoutines\": [\n                        {\n                            \"name\": \"cow_cookie:cookie/1\"\n                        }\n                    ],\n                    \"repo\": \"https://github.com/ninenines/cowlib\",\n                    \"vendor\": \"ninenines\",\n                    \"versions\": [\n                        {\n                            \"lessThan\": \"c17fd73945ef536cccecc492d286fb6b6d1c3307\",\n                            \"status\": \"affected\",\n                            \"version\": \"f017f8a0ecbffd5033d9ab49bf180186f7a523a7\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","vector":"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","score":2.1,"severity":"LOW"}],"references":["https://github.com/erlef/cowlib/commit/177953dd51540da11090666c1f007214127a1144","https://cna.erlef.org/cves/CVE-2026-43969.html","https://osv.dev/vulnerability/EEF-CVE-2026-43969","https://github.com/ninenines/cowlib/commit/f017f8a0ecbffd5033d9ab49bf180186f7a523a7","https://github.com/ninenines/cowlib/commit/c17fd73945ef536cccecc492d286fb6b6d1c3307"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-43969","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-43969","identifiers":["CVE-2026-43969"]},"retained":false,"historicalAffected":[]}],"coverage":[]}