Bug 2495858 (CVE-2026-56016)

Summary: CVE-2026-56016 perl-CGI-Session: perl-CGI-Session: Authentication bypass via predictable session IDs
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: high    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in perl-CGI-Session. This vulnerability allows a remote attacker to predict session identifiers due to the use of low-entropy sources in the `generate_id` method. By predicting a session identifier, an attacker can impersonate a user's session, leading to a bypass of authentication mechanisms and potential unauthorized access to sensitive information or functionality.
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Bug Depends On: 2495886    
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Description OSIDB Bzimport 2026-07-01 09:01:27 UTC 
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.