CVE-2026-5081
CriticalCVSS 9.1Exploitation Probability (EPSS)
Low risk22th percentile — higher than 22% of all known CVEs
Summary
The vulnerability in the Apache::Session::Generate::ModUniqueId library versions 1.54 through 1.94 for Perl causes session IDs to be generated based on the UNIQUE_ID environment variable from the Apache mod_unique_id module. The ID relies on the IPv4 address, process ID, epoch time, a 16-bit counter, and a thread index, with no obfuscation, making it predictable and unsuitable for security purposes.
Risk Assessment
An attacker can predict or reconstruct session IDs, enabling session hijacking, data theft, or unauthorized system access. The risk is especially high when the server is publicly accessible and data such as the server IP address or timestamps are easily obtainable.
Recommendation
Immediately update the Apache::Session::Generate::ModUniqueId library to version 1.95 or later, which includes a security fix. If an update is not possible, switch to a more secure session ID generator, such as Apache::Session::Generate::MD5.
Original NVD description (English source)
Apache::Session::Generate::ModUniqueId versions from 1.54 through 1.94 for Perl session ids are insecure. Apache::Session::Generate::ModUniqueId (added in version 1.54) uses the value of the UNIQUE_ID environment variable for the session id. The UNIQUE_ID variable is set by the Apache mod_unique_id plugin, which generates unique ids for the request. The id is based on the IPv4 address, the process id, the epoch time, a 16-bit counter and a thread index, with no obfuscation. The server IP is often available to the public, and if not available, can be guessed from previous session ids being issued. The process ids may also be guessed from previous session ids. The timestamp is easily guessed (and leaked in the HTTP Date response header). The purpose of mod_unique_id is to assign a unique id to requests so that events can be correlated in different logs. The id is not designed, nor is it suitable for security purposes.