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Keycloak's missing timestamp validation allows attackers to extend SAML response validity periods

Low severity GitHub Reviewed Published Jan 26, 2026 to the GitHub Advisory Database • Updated Jan 27, 2026

Package

maven org.keycloak:keycloak-services (Maven)

Affected versions

<= 26.5.2

Patched versions

None

Description

A flaw was found in Keycloak's SAML brokering functionality. When Keycloak is configured as a client in a Security Assertion Markup Language (SAML) setup, it fails to validate the NotOnOrAfter timestamp within the SubjectConfirmationData. This allows an attacker to delay the expiration of SAML responses, potentially extending the time a response is considered valid and leading to unexpected session durations or resource consumption.

References

Published by the National Vulnerability Database Jan 26, 2026
Published to the GitHub Advisory Database Jan 26, 2026
Reviewed Jan 27, 2026
Last updated Jan 27, 2026

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(15th percentile)

Weaknesses

Missing XML Validation

The product accepts XML from an untrusted source but does not validate the XML against the proper schema. Learn more on MITRE.

Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data. Learn more on MITRE.

Insufficient Session Expiration

According to WASC, Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization. Learn more on MITRE.

CVE ID

CVE-2026-1190

GHSA ID

GHSA-63v5-26vq-m4vm

Source code

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