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Description

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.

PUBLISHED Reserved 2026-01-15 | Published 2026-01-15 | Updated 2026-01-15 | Assigner redhat




LOW: 3.7CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Problem types

Improper Input Validation

Product status

Default status
affected

Default status
affected

Default status
affected

Default status
affected

Default status
affected

Default status
affected

Default status
affected

Timeline

2026-01-15:Reported to Red Hat.
2026-01-15:Made public.

Credits

Red Hat would like to thank Alexander Schwartz (RedHat) for reporting this issue.

References

access.redhat.com/security/cve/CVE-2026-0976 vdb-entry

bugzilla.redhat.com/show_bug.cgi?id=2429869 (RHBZ#2429869) issue-tracking

cve.org (CVE-2026-0976)

nvd.nist.gov (CVE-2026-0976)

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