CVE-2026-75870 (GCVE-0-2026-75870)

Vulnerability from cvelistv5 – Published: 2026-08-22 13:35 – Updated: 2026-08-25 19:28
VLAI
Title
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
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. 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.
Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 19:27 UTC
CWE
  • CWE-1394 - Use of Default Cryptographic Key
Assigner
CPANSec CNA
References
Impacted products
Vendor Product Version
Affected: 0 , < 0.18 (custom)
Show details on NVD website
To clipboard 

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