CVE-2026-50012
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Heap-based Buffer Overflow in Squid Proxy Cache

Publication date: 2026-07-16

Last updated on: 2026-07-16

Assigner: GitHub, Inc.

Description
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.

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Meta Information

Published
2026-07-16
Last Modified
2026-07-16
Generated
2026-07-16
AI Q&A
2026-07-16
EPSS Evaluated
N/A
NVD
CVE-2026-50012
EUVD
EUVD-2026-44961

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
squid squid to 7.6 (inc)
squid squid to 7.6 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-122 A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

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Executive Summary

CVE-2026-50012 is a heap-based buffer overflow vulnerability in Squid Proxy Cache versions prior to 7.6. It occurs due to improper input validation in cache digest reply handling. A trusted peer can send a maliciously crafted reply to a cache digest request message, causing the on-the-wire size of the cache digest to exceed the declared mask size. This triggers a buffer overflow in the peer_digest.cc file.

Detection Guidance

To detect this vulnerability, check if your Squid instance is running a version prior to 7.6 and was compiled with --enable-cache-digests. Inspect Squid logs for unusual activity related to cache digest handling or peer connections. Monitor network traffic for malformed cache digest replies from trusted peers.

Impact Analysis

This vulnerability can impact availability by causing crashes or service disruptions in Squid instances. It may also allow attackers to execute arbitrary code or gain unauthorized access if exploited. The impact is limited to Squid instances compiled with --enable-cache-digests and configured with cache_peer entries.

Compliance Impact

This vulnerability does not directly impact compliance with GDPR or HIPAA as it is a technical flaw in Squid Proxy Cache's cache digest handling. However, if exploited, it could lead to service disruption or unauthorized data access, which may indirectly affect compliance by compromising system integrity or availability.

Mitigation Strategies

Upgrade Squid to version 7.6 or later. If upgrading is not possible, apply patches from the Squid project. Disable cache digests for untrusted peers or audit configurations to ensure all cache peers are trusted. Monitor for suspicious activity in logs.

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