CVE-2026-110931
Description
A flaw was found in the SAML 1.1 assertion parser of Keycloak, a tool used for identity and access management. The issue occurs when the parser handles a specific element called AuthorityBinding within an authentication statement. Due to an incomplete fix for a previous vulnerability, the parser can enter an infinite loop that consumes all available memory, causing the entire Keycloak service to crash and become unavailable to users.
Statement
The Red Hat Product Security team has assessed the severity of this vulnerability as Important, given that it can be exploited by a remote, unauthenticated attacker with a single request. Successful exploitation allows an attacker to cause a complete Denial of Service by terminating the JVM via memory exhaustion. The vulnerability's root cause is an infinite loop in the SAML 1.1 AuthorityBinding parsing logic, which was missed during the remediation of CVE-2026-7307.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
--- CME Mitigation Guidance (2026-11-06) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to advance parser state past AuthorityBinding elements during SAML 1.1 AuthenticationStatement processing in keycloak-saml-core to halt unbounded heap allocation: upgrade to Keycloak 26.4.17, 26.6.8 (or the fixed Rhbk/Keycloak Rhel/Keycloak Services builds), which advance the parser past AuthorityBinding child elements during SAML 1.1 AuthenticationStatement processing, closing all 2 injection vectors (crafted SAML request to realm SAML endpoint, crafted SAML request to SAML identity provider broker endpoint). Until patched, this is a concern on Keycloak deployments exposing realm SAML endpoints or SAML identity provider broker endpoints, so Restrict network access to Keycloak realm SAML endpoints and SAML identity provider broker endpoints to trusted networks and identity providers. As a compensating measure, Configure systemd WatchdogSec and Restart directives to automatically restart Keycloak following JVM OutOfMemoryError termination and Monitor cgroup memory.events and PSI metrics to detect anomalous memory pressure and rapid heap exhaustion. These controls limit blast radius and contain exploitation, but they do not fix the underlying SAML 1.1 parser infinite loop defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-1204 Service Watchdog and Automatic Restart (systemd WatchdogSec/Restart) (medium)
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Amplification
An infinite loop will cause unexpected consumption of resources, such as CPU cycles or memory. The software's operation may slow down, or cause a long time to respond.
Acknowledgements
Red Hat would like to thank Animesh Roy for reporting this issue.
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