CVE-2021-22958

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-10-07 · updated 2026-06-17
Weakness: CWE-918

Description

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

Concrete CMS: before 8.5.5 — fixed in 8.5.5

How to fix

Upgrade to a fixed version: Concrete CMS 8.5.5. Check the vendor advisory for mitigations.

References

https://documentation.concretecms.org/developers/introduction/version-history/855-release-notes
https://hackerone.com/reports/863221
https://documentation.concretecms.org/developers/introduction/version-history/855-release-notes
https://hackerone.com/reports/863221

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