CyberSecBulletin
CVE-2026-2603NVD status: Analyzed

Red Hat build of Keycloak 26.2: Missing Authentication for Critical Functionality

Published Updated By the CyberSecBulletin desk

CVE-2026-2603 is a high-severity missing authentication for critical functionality vulnerability in Red Hat build of Keycloak 26.2 from Red Hat, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. There is no confirmed exploitation so far. EPSS estimates a 0.5% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Build Of Keycloak to 26.2.14 or 26.4.10, whichever matches your release line, or a later version.
  2. Read the advisory on access.redhat.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
Red HatRed Hat build of Keycloak 26.2Not specified in the recordNot stated
Red HatRed Hat build of Keycloak 26.2.14Not specified in the recordNot stated
Red HatRed Hat build of Keycloak 26.4Not specified in the recordNot stated
Red HatRed Hat build of Keycloak 26.4.10Not specified in the recordNot stated
Red HatBuild Of Keycloak26.2 up to, but not including, 26.2.14; 26.4 up to, but not including, 26.4.1026.2.14, 26.4.10

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N. Scored by CNA (redhat.com).

Scoring systemScoreSeverityScored by
CVSS 3.18.1HighCNA (redhat.com)
CVSS 3.18.1HighCNA

Official description

A flaw was found in Keycloak. A remote attacker could bypass security controls by sending a valid SAML response from an external Identity Provider (IdP) to the Keycloak SAML endpoint for IdP-initiated broker logins. This allows the attacker to complete broker logins even when the SAML Identity Provider is disabled, leading to unauthorized authentication.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Missing Authentication for Critical Functionality

The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.

How developers prevent this class of flaw

  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using libraries with authentication capabilities such as OpenSSL or the ESAPI Authenticator.
  • When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to require strong authentication for users who should be allowed to access the data.

More Missing Authentication for Critical Functionality vulnerabilities (CWE-306)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Red Hat build of Keycloak 26.2

All Red Hat build of Keycloak 26.2 vulnerabilities

Recent Missing Authentication for Critical Functionality vulnerabilities

Spotted an error? Tell us.