CVE-2026-90997: keycloak Authentication Bypass by Capture-replay

Vulnerability summary

CVE-2026-90997 is a high (CVSS 7.4) Authentication Bypass by Capture-replay vulnerability in keycloak. EPSS estimates a 0.40% chance of exploitation in the next 30 days, higher than 32.4% of scored vulnerabilities.

Timeline

1. 17-09-2026
   PublishedVulnerability first disclosed.
2. 25-09-2026
   Last modifiedVulnerability information updated.

Description

A flaw was found in Keycloak. When deployed in stateless mode with MySQL or MariaDB, a mismatch in row-count semantics between the database driver and Keycloak's application logic allows an attacker to bypass replay protection. This vulnerability enables an attacker who intercepts single-use security artifacts, such as JWT client assertions, DPoP proofs, or one-time password (TOTP) codes, to replay them. Successful exploitation grants unauthorized access to the token endpoint or login flow.

• CWE-294Authentication Bypass by Capture-replayA capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes).