Squid 4 End of Life Date
Squid 4 end-of-life date, support status, and CVE risk. Data from endoflife.date and official vendor documentation.
Squid 4 was released on July 3, 2018 and support ended on October 4, 2021 — a supported lifespan of 3 years and 3 months, longer than the 2 years and 9 months median for Squid releases. The last patch it will ever receive is 4.17, published October 4, 2021 — on the day support ended. It has been without security patches for 4 years and 10 months. 2 newer Squid releases have shipped since.
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When Squid 4 reaches end of life, the maintainers stop issuing security patches for this version. CVEs discovered after the EOL date are publicly disclosed on the National Vulnerability Database with no patch available. Exploit code frequently appears on GitHub within days of disclosure.
The CVE blind spot: Most vulnerability scanners check for known CVEs but do not flag the ongoing accumulation of unpatched vulnerabilities in EOL software versions. Running Squid 4 past its EOL date creates a permanently growing attack surface that standard security tooling will not surface.
Migrate to Squid 7 or implement compensating controls — network segmentation, enhanced monitoring, restricted access — while migration is underway.