CVE-2026-75870None▾ SunlitPunk 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 secr…
▾ Sunlit zone — Low / medium · no exploitation signal
impact 2.8 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Aug 23.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
0.2%
0.2% → 0.5%
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.
Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Connected by shared product, vendor, weakness, or advisory.