Medium [CVE-2026-50012] memory corruption in cache_digest reply handling
This medium-severity Red Hat Linux advisory covers CVE-2026-50012 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
Squid is a caching proxy for the Web.
Prior to 7.6, due to an improper input validation bug in cache digest reply handling (peerDigestSwapInMask in src/peer_digest.cc), Squid is vulnerable to a heap-based buffer overflow: a cache digest's on-the-wire size may be larger than the mask_size declared within the digest, so a trusted peer sending a maliciously crafted reply to a cache_digest request message can trigger the overflow.
This attack is limited to Squid instances compiled with the --enable-cache-digests option and configured with cache_peer entries. This issue is fixed in version 7.6.
A flaw was found in Squid. This issue allows a trusted server to cause a denial of service when sending specially crafted replies to cache_digest request messages.
To exploit this issue, an attacker must control a trusted cache peer server. Also, cache digests are not enabled in the default configuration.
Squid deployments that do not use cache peering are not affected. Furthermore, even those that do are only vulnerable when the attacker controls a configured peer server within the same administrative domain.
A compromised peer can reliably crash the Squid process via a heap-based buffer overflow during digest exchange, but code execution faces considerable practical security barriers.
- < 7.6
Official advisory · high-confidence parse· fetched 15 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 15 days ago·verify at source
Mitigation checklist
- To mitigate this vulnerability, restrict or disable cache digest processing for cache peers by adding the appropriate settings to the squid.conf configuration file: Disable cache digests for any cache_peer not under direct control by adding the no-digest option. This completely removes the vulnerability for those peers at the cost of increased bandwidth. Use of HTCP or ICP as alternative protocols can reduce that cost. ~~~ # Example of disabling digests for an untrusted peer. cache_peer untrusted.server.example.com parent 3128 3130 no-digest ~~~ Audit the Squid configuration and ensure that all configured cache_peer entries are under direct control and are trusted. Restricting cache peering exclusively to trusted domains greatly reduces the risk of exploitation. ~~~ # Example of a fully trusted peer without the no-digest flag. cache_peer trusted.internal.example.com parent 3128 3130 ~~~
Official advisory · high-confidence parse· fetched 15 days ago·verify at source
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