CVE-2026-75870 — 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
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. The session keyword freezes its optio…
Published: 2026-08-22 · CVSS: 9.1 · CVSS 3.1
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. The 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. An 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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7