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.
The module uses the value of the UNIQUE_ID environment variable set by the Apache mod_unique_id plugin as the session identifier. This value is constructed based on the server's IPv4 address, process identifier, epoch time, a 16-bit counter, and thread index — without any masking or random element. The server's IP address is often publicly available or can be guessed based on previously obtained session identifiers. The timestamp is easy to predict, and is additionally disclosed in the HTTP response header (Date). Process identifiers can also be inferred from previous session identifiers.
An attacker can predict or reproduce valid session identifiers of other users, thereby gaining unauthorized access to their sessions (session hijacking) and associated data and permissions.
Discontinue using the Apache::Session::Generate::ModUniqueId module as a session identifier generator. The vendor recommends switching to Apache::Session::Generate::Random, which generates cryptographically secure session identifiers. Apply patches available from the vendor according to the references.
Apache::Session::Generate::ModUniqueId for Perl in versions 1.54 through 1.94 (inclusive).
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NChorny Apache\
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