CVE-2026-16093
MEDIUMDescription
Keycloak provides a mechanism called Client Policies to enforce security requirements on clients, such as requiring them to use signed JWTs for authentication. A flaw was discovered where this enforcement can be bypassed. An attacker with valid client credentials can provide a fake, unsigned assertion header that tricks the system into thinking the policy requirements have been met. This allows the attacker to authenticate using simpler methods like a client secret even when the administrator has mandated more secure, signed assertions.
How to fix
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
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Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 33% of all known CVEs.
References
Related Vulnerabilities
Other CWE-807 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2026-34486 | High | 7.5 | 99% | KEV | Fix |
| CVE-2026-21509 | High | 7.8 | 73% | KEV | Fix |
| CVE-2024-13974 | High | 8.1 | 7.4% | - | Fix |
| CVE-2021-41129 | High | 8.1 | 1.8% | - | Fix |
| CVE-2026-21514 | High | 7.8 | 1.5% | KEV | - |
| CVE-2025-49827 | Critical | 9.8 | 1.4% | - | Fix |
Common questions
How do I fix CVE-2026-16093?
Published advisories record a fix for 2 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-16093 being actively exploited?
Not that we know of. CVE-2026-16093 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.39% is the estimated probability that it will be exploited in the next 30 days. That is higher than 33% of all scored CVEs.
How severe is CVE-2026-16093?
CVE-2026-16093 has a CVSS v3 base score of 5.4, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-16093 affect?
Published advisories record a fix for rhbk/keycloak (Rocky), rhbk/keycloak (Red Hat / RHEL). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-16.