CVE-2026-59139 is an out-of-bounds read vulnerability in Data::ReqRep::Shared versions prior to 0.05. The reqrep_recv_locked function performs a memcpy using offset and length values read directly from a memory-mapped file segment without bounding them against the arena capacity. Although the header is validated at attach time, the array contents controlling the copy are not validated, allowing a local attacker with write access to the backing file to craft malicious offset and length values. This can lead to reading memory beyond the intended buffer or crashing the process.

An attacker with local write access to the backing file can cause the application to read memory out-of-bounds or crash, potentially leading to denial of service or information disclosure. The CVSS score of 9.1 reflects a critical severity with network attack vector, low attack complexity, no privileges required, no user interaction, high confidentiality impact, no integrity impact, and high availability impact.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict local write access to the backing file to trusted users only to prevent exploitation.