Medium [CVE-2026-18218] Client not-before revocation ignored when realm not-before is older but nonzero
This medium-severity Red Hat Linux advisory covers CVE-2026-18218 affecting Red Hat Build of Keycloak.
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Summary
A flaw was found in the TokenManager component of the Keycloak identity management service. When an administrator attempts to revoke tokens for a specific application (client) using a "not-before" policy, the revocation may be silently ignored if the overall security realm already has an older, non-zero revocation policy in place.
This issue can allow previously issued tokens to remain valid for refreshing sessions and accessing user information even after an administrator has attempted to invalidate them. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires a specific pre-existing realm configuration and the possession of valid tokens issued within a specific timeframe.
Successful exploitation allows an attacker to continue using revoked tokens for refresh, introspection, and UserInfo requests. The vulnerability's root cause is a logic error in the TokenManager.
NotBeforeCheck function that fails to correctly enforce client-specific revocation policies when a realm-level policy is also present. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Red Hat severity: Moderate — CVSS 4.2 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N). Weakness: CWE-862.
Affected Red Hat products: Red Hat Build of Keycloak.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
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