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Vulnerabilities

Vulnerability · CVE-2026-11800

Keycloak has authentication bypass via jwt algorithm confusion

Published Nov 3, 2026 · catalog updated Nov 3, 2026 · Keycloak has authentication bypass

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-11800. EPSS is 0.30%. Act only if a listed version of Keycloak has authentication bypass is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Keycloak has authentication bypass).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.30%
Remediation
Version ranges on file
Affected products
maven org.keycloak · maven org.keycloak:keycloak-services

### Description A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized access and potential privilege escalation.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • maven org.keycloakversion unspecified
  • maven org.keycloak:keycloak-services< 26.6.4

How to fix CVE-2026-11800

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-11800. EPSS is 0.30%. Act only if a listed version of Keycloak has authentication bypass is installed.

Which versions are affected?

Compare what you have installed with < 26.6.4. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-347: Improper Verification of Cryptographic Signature. EPSS 0.30%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Keycloak security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Nov 3, 2026 · GitHub Advisory Database

    Detected

    ### Description A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to un

  2. Nov 3, 2026 · GitHub Advisory Database

    Updated

    ### Description A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to un

Sources

  • CVE.orgVulnerability recordCVE-2026-11800

    Official CVE identifier

    cve.org
  • GitHub Advisory DatabasePackage advisoryGHSA-j97h-3f8r-mrjr

    Keycloak has authentication bypass via jwt algorithm confusion

    github.com
  • GitLab Advisory DatabasePackage advisoryCVE-2026-11800

    A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized acces

    advisories.gitlab.com

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • GitLab Advisory DatabaseNov 6, 2026
  • GitHub Advisory DatabaseNov 6, 2026
  • CVE.orgNov 4, 2026