CVE-2026-82965
Description
A flaw was found in the SAML implementation of Keycloak, an open-source identity and access management solution. The SAML Artifact Resolution and ECP SOAP endpoints do not properly limit the size or complexity of incoming XML requests. An unauthenticated remote attacker can exploit this by sending specially crafted, large XML messages that cause the server to consume excessive memory. This leads to the application running out of memory and crashing, resulting in a denial of service for all users.
Statement
The Red Hat Product Security team has assessed the severity of this vulnerability as Important, given that it can be exploited by an unauthenticated remote attacker. Successful exploitation allows an attacker to cause a complete denial of service by crashing the Keycloak process. The vulnerability's root cause is the lack of proper size and element count validation for XML payloads processed by the SAML SOAP endpoints.
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 enforce XML payload size and element count validation during SAML SOAP request parsing before DOM tree construction: upgrade to Red Hat build of Keycloak 26.4.17, 26.6.8 (or the corresponding fixed Red Hat builds), which enforce XML payload size and element count limits when parsing incoming SAML SOAP requests, closing all 2 injection vectors (SAML Artifact Resolution SOAP requests with large or deeply nested XML payloads, SAML ECP SOAP requests containing millions of empty XML elements). Until patched, this is a concern on Keycloak deployments exposing SAML SOAP endpoints to unauthenticated network access, so Restrict network access to SAML SOAP endpoints such as /realms/{realm}/protocol/saml/resolve to trusted internal clients and reverse proxies. As a compensating measure, Configure systemd service watchdog and automatic restart directives to detect OutOfMemoryError process exits and restore Keycloak service availability and Implement rate limiting and connection throttling on SOAP requests targeting the SAML resolve endpoint to mitigate rapid heap exhaustion. These controls limit blast radius and contain exploitation, but they do not fix the underlying unbounded XML parsing 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: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
If an attacker can trigger the allocation of the limited resources, but the number or size of the resources is not controlled, then the most common result is denial of service. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment, i.e., the product may slow down, crash due to unhandled errors, or lock out legitimate users. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
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