CVE-2026-0976: Keycloak has an improper input validation vulnerability

January 15, 2026 (updated October 23, 2026)

A flaw was found in Keycloak. This improper input validation vulnerability occurs because Keycloak accepts RFC-compliant matrix parameters in URL path segments, while common reverse proxy configurations may ignore or mishandle them. A remote attacker can craft requests to mask path segments, potentially bypassing proxy-level path filtering. This could expose administrative or sensitive endpoints that operators believe are not externally reachable.

References

access.redhat.com/errata/RHSA-2026:2365
access.redhat.com/security/cve/CVE-2026-0976
bugzilla.redhat.com/show_bug.cgi?id=2429869
github.com/advisories/GHSA-v897-pv23-r8cw
nvd.nist.gov/vuln/detail/CVE-2026-0976

Code Behaviors & Features

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