Solr 4 end-of-life date, support status, and CVE risk. Data from endoflife.date and official vendor documentation.
When Solr 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 Solr 4 past its EOL date creates a permanently growing attack surface that standard security tooling will not surface.
Migrate to Solr 10 or implement compensating controls — network segmentation, enhanced monitoring, restricted access — while migration is underway.