The vulnerability in Data::RingBuffer::Shared (CVE-2026-65066) involves the creation of a mmap backing file with mode 0666, which under default umask results in a world-readable file (0644). The file is opened without O_EXCL and O_NOFOLLOW flags, allowing an attacker to pre-create or symlink the file path to redirect the open operation. This occurs in versions prior to 0.04. Because the shared segment resides in directories like /tmp or /dev/shm, any local user can read the IPC payloads, leading to information disclosure. The issue is classified under CWE-732 (Incorrect Permission Assignment) and CWE-59 (Improper Link Resolution).

Local attackers can read sensitive inter-process communication data due to world-readable permissions on the mmap backing file. They can also exploit race conditions or symlink attacks to redirect file access, potentially gaining unauthorized read access to IPC payloads. There is no indication of integrity or availability impact. The CVSS score is 3.8 (low severity), reflecting limited impact and local attack vector with low privileges required.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, users should avoid running vulnerable versions or restrict local user access to the shared directories where the mmap files are created. Applying stricter file permission policies and ensuring secure file open flags (O_EXCL and O_NOFOLLOW) are used can mitigate the risk.