CVE-2026-50012 describes a heap-based buffer overflow in squid-cache versions before 7.6 caused by improper input validation in the cache digest reply handling code (peerDigestSwapInMask in src/peer_digest.cc). Specifically, the size of a cache digest received over the network can be larger than the declared mask_size, allowing a trusted peer to trigger a buffer overflow by sending a maliciously crafted reply to a cache_digest request. This vulnerability only affects Squid instances compiled with the --enable-cache-digests option and configured with cache_peer entries. The issue is resolved in Squid version 7.6.

The vulnerability allows a trusted peer to cause a heap-based buffer overflow, which can result in denial of service or potentially other impacts related to memory corruption. The CVSS 3.1 base score is 5.5 (medium severity), reflecting network attack vector, low attack complexity, required high privileges, no user interaction, unchanged scope, no confidentiality impact, low integrity impact, and high availability impact.

Upgrade to Squid version 7.6 or later, where this vulnerability is fixed. If upgrading is not immediately possible, ensure that Squid is not compiled with the --enable-cache-digests option or that cache_peer entries are not configured, as the vulnerability requires both conditions. Patch status is not explicitly stated beyond the fix in version 7.6; check the vendor advisory for the latest remediation guidance.