CVE-2021-22958: Concretecms Concrete CMS

Critical severity, CVSS 9.8. EPSS: 1.2% chance of exploitation in the next 30 days.

A Server-Side Request Forgery vulnerability was found in concrete5 < 8.5.5 that allowed a decimal notation encoded IP address to bypass the limitations in place for localhost allowing interaction with local services. Impact can vary depending on services exposed.CVSSv2.0 AV:A/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N

Affected products

• Concretecms Concrete CMS: before 8.5.5 (fixed in 8.5.5)

Published 2021-10-07. Last modified 2026-06-17.