{"id":"CVE-2026-75870","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-75870","summary":"Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret.\n\nThe session keyword freezes its options onto…","details":"Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret.\n\nThe session keyword freezes its options onto the application as given: it does not require a secret, warn, or refuse to start when one is absent. The cookie read and the write-back both default that key to the empty string, so a declaration with no secret option, or with an undefined or empty one, signs and verifies with a zero-length HMAC-SHA256 key.\n\nAn attacker who knows the cookie format can then mint one offline carrying any contents the session holds, such as a user identifier or a role. Nothing marks the misconfiguration at runtime: cookies are well formed and sessions round-trip as expected.","published":"2026-08-22T14:16:33.813","modified":"2026-08-25T20:17:05.067","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":null,"references":[{"type":"WEB","url":"https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h"},{"type":"WEB","url":"https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm"},{"type":"WEB","url":"https://metacpan.org/release/LNATION/Punk-0.18/source/Changes"},{"type":"WEB","url":"http://www.openwall.com/lists/oss-security/2026/08/22/5"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-08-25T20:17:05.067"}}