Apache::Session::Generate::SHA256 prior to version 1.3.19 generates session identifiers by hashing predictable inputs including the built-in rand() output, epoch time, and process ID. These low-entropy sources result in session IDs that can be predicted by attackers, undermining session security. Although version 1.3.19 attempts to use a more secure method, it falls back to the insecure method if Crypt::URandom::urandom fails, but this fallback is unlikely to be triggered due to Crypt::URandom being a hard requirement. This vulnerability is categorized under CWE-340 (Generation of Predictable Numbers or Identifiers) and CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator). No known exploits are reported in the wild.

The vulnerability allows attackers to predict session IDs generated by the affected module, potentially enabling unauthorized access to user sessions or systems relying on these session identifiers. The impact is limited to confidentiality and integrity, with no reported impact on availability. The CVSS score of 6.5 reflects a medium severity with network attack vector, low attack complexity, no privileges or user interaction required, and partial confidentiality and integrity impact.

No official patch or remediation level has been published by the vendor at this time. Users should monitor the vendor advisory for updates. Since version 1.3.19 attempts to use a more secure method with a fallback to the insecure method only if Crypt::URandom::urandom fails, ensuring that Crypt::URandom is properly installed and functional may mitigate fallback risks. Consider avoiding use of affected versions or implementing additional session security controls until an official fix is released.