CVE-2026-4634
Redhat Build Of Keycloak 26.2 … 26.4.11
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2026-4634 is a high-severity Excessive Platform Resource Consumption within a Loop (CWE-1050) vulnerability in Redhat Build Of Keycloak. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 41th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SC-6 (Resource Availability) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-4634 is a denial-of-service (DoS) vulnerability in Keycloak, published on 2026-04-02. The flaw allows an unauthenticated attacker to send a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This triggers high resource consumption and prolonged processing times on the Keycloak server. The issue has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and maps to CWE-1050.
An unauthenticated attacker with network access to the Keycloak server can exploit this vulnerability remotely with low complexity and no privileges required. By submitting the malicious request, the attacker causes significant resource exhaustion, leading to degraded performance or complete DoS, disrupting authentication and authorization services for legitimate users.
Red Hat has addressed this vulnerability in multiple security errata, including RHSA-2026:6475, RHSA-2026:6476, RHSA-2026:6477, and RHSA-2026:6478. Additional details on the CVE, including mitigation and patch information, are available at https://access.redhat.com/security/cve/CVE-2026-4634.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-18212
Vulnerability Data
A flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high resource consumption and…
more
prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 2 hardening rules · 2 OS baselines
V2.4.1V7.6.2V15.4.3V15.4.4
Mitigating Controls (NIST 800-53 r5) AI
SA-11 developer testing can discover loops that consume platform resources before deployment.
SC-6 directly protects resource availability by enforcing allocation limits that bound consumption from faulty loops.
AC-10 caps concurrent sessions, reducing blast radius when a loop consumes session or connection resources.
SC-5 limits effects of DoS events that can result from unbounded resource consumption inside loops.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Runtime monitoring can detect excessive resource use from loops as an adverse event.
Capacity monitoring and resource management directly limit impact of runaway consumption.
Secure SDLC practices can prevent introduction of unbounded loops during development.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Monitoring can alert on resource abuse but does not eliminate the coding flaw.
Security testing can discover the defect but does not remove it from production code.
Redundancy can absorb some resource spikes but does not prevent the loop defect.
Logging may detect excessive consumption but does not stop the loop.
Secure SDLC processes can catch the weakness during reviews but do not inherently prevent it.
Secure coding standards explicitly forbid resource-consuming loops.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 9 (1 rule)
- V-271709 OL 9 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. prevents CWE-1050
RHEL 9 (1 rule)
- V-257995 RHEL 9 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. prevents CWE-1050