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CVE-2026-16093

Keycloak-services: keycloak-services: required signed-jwt assertion policy can be bypassed with unsigned assertion headers

No known exploitation. EPSS puts it in the 31st percentile. A vendor fix is available.

CVSS 3.15.4MediumEPSS percentile31st0.4% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFixVendor fixNo build named by the sources

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

The vendor has published a fix. Version details are below where the sources state them.

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

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.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS31st
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.4% chance of exploitation activity in the next 30 days, which ranks it in the 31st percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

9 events over 63 days, from the signal feeds we watch.

  1. Patch availablerecord updated
  2. Patch availablerecord updated
  3. Record updated
  4. Publishedweakness classified, record updated
  5. OpenVAS check added

Affected products

And 1 more affected product. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 5.4 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity LowNo special conditions — the attack can be reliably reproduced
  • Privileges Required LowRequires basic user-level privileges
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality LowSome restricted information is disclosed, but limited in scope
  • Integrity LowData modification is possible but limited in scope or consequence
  • Availability NoneNo availability impact

Weaknesses

Sources

References in the record

And 1 more reference. See all after sign-in

Watch the software you run.

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We'll flag the next CVE, public exploit or patch for Build Of Keycloak, not every advisory.

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