High [CVE-2026-56016] Authentication bypass via predictable session IDs

CGI::Session::ID::md5 versions before 4.49 for Perl generate predictable session ids from low-entropy sources. The generate_id method builds the session id from a MD5 digest of the process id, the epoch time, and the built-in rand() function.

All three are predictable, low-entropy sources: the PID is drawn from a small range, the epoch time can be guessed or read from the HTTP Date header, and Perl's rand() is unsuitable for security purposes because it is predictable and reversible. An attacker who predicts a session id can impersonate the corresponding session and bypass authentication.

This vulnerability allows a remote attacker to predict session identifiers due to the use of low-entropy sources in the `generate_id` method. This Important flaw in perl-CGI-Session allows a remote attacker to bypass authentication by predicting session identifiers.

This predictability enables an attacker to impersonate a user's session, potentially leading to unauthorized access in web applications utilizing this module for session management. Red Hat severity: Important — CVSS 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N).

Weakness: CWE-331. Affected Red Hat products: Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7.

Red Hat does not currently list a fixing RHSA for this CVE.

Affected products named by the advisory: Red Hat package: perl-cgi-session.