CVE-2026-1190 identifies a security vulnerability in the Red Hat build of Keycloak version 26.4, specifically within its Security Assertion Markup Language (SAML) brokering functionality. Keycloak acts as a client in SAML federated authentication setups, where it processes SAML responses containing assertions about user identity and session validity. The vulnerability arises because Keycloak fails to validate the NotOnOrAfter timestamp within the SubjectConfirmationData element of the SAML response. This timestamp is intended to specify the expiration time of the assertion, ensuring that the authentication token is only valid for a limited period. By not enforcing this validation, an attacker can manipulate or delay the expiration time, effectively extending the validity of a SAML response beyond its intended lifetime. This can lead to prolonged session durations, allowing users or attackers to maintain authenticated sessions longer than expected, potentially bypassing session expiration controls. Additionally, extended session validity may cause increased resource consumption on the Keycloak server due to prolonged session management. The vulnerability does not directly compromise confidentiality or availability but impacts integrity by undermining the intended session expiration mechanism. Exploitation requires network access to the Keycloak server and user interaction to trigger the acceptance of manipulated SAML responses. The attack complexity is high, as it involves crafting valid SAML responses with altered timestamps. No known exploits have been reported in the wild, and no patches or fixes are currently linked. The CVSS v3.1 base score is 3.1, indicating a low severity level primarily due to limited impact and exploitation difficulty.

The primary impact of CVE-2026-1190 is the potential extension of authenticated session durations beyond their intended expiration, which can undermine session management policies. This may allow unauthorized prolonged access if an attacker can manipulate SAML responses or if legitimate users retain sessions longer than expected, increasing the risk of session hijacking or misuse. Extended sessions can also lead to resource exhaustion on authentication servers, potentially degrading performance or availability indirectly. While confidentiality is not directly affected, the integrity of session expiration controls is compromised. Organizations relying on Keycloak for SAML-based authentication, especially in environments with strict session timeouts or regulatory requirements for session management, may face compliance risks. The vulnerability's exploitation complexity and requirement for user interaction limit widespread exploitation, but targeted attacks against high-value systems using Keycloak could leverage this flaw to maintain persistent access.

To mitigate CVE-2026-1190, organizations should implement the following specific measures: 1) Monitor Red Hat and Keycloak vendor advisories closely for patches or updates addressing this vulnerability and apply them promptly once available. 2) Review and harden SAML configurations in Keycloak, ensuring strict validation of all SAML assertion elements, including timestamps, using custom validation logic if necessary. 3) Implement additional session management controls outside of SAML assertions, such as server-side session expiration timers and re-authentication requirements after defined intervals. 4) Employ network-level protections to restrict access to Keycloak servers, limiting exposure to trusted clients and reducing attack surface. 5) Enable detailed logging and monitoring of SAML authentication events to detect anomalies such as unusually long session durations or repeated authentication attempts with delayed timestamps. 6) Educate administrators and developers about the risks of improper SAML validation and encourage secure coding and configuration practices. 7) Consider deploying Web Application Firewalls (WAFs) or SAML-specific security gateways capable of validating assertion timestamps independently. These steps go beyond generic advice by focusing on compensating controls and proactive monitoring until an official patch is available.