Cyber Resilience

CVE-2026-9087

MediumUpdated

Published: 20 May 2026

Published
20 May 2026
Modified
26 June 2026
KEV Added
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Patch
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CVSS Score v3.1 6.4 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N
EPSS Score 0.0031 22.9th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-9087 is a medium-severity Authorization Bypass Through User-Controlled Key (CWE-639) vulnerability in Redhat Build Of Keycloak. Its CVSS base score is 6.4 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Account Manipulation (T1098); ranked at the 22.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access Control

EU & UK References

Vulnerability details

A flaw was found in Keycloak. The cross-session verification proof is keyed only by (local userId, idpAlias) and is not bound to the upstream identity that was actually verified, so a second upstream account on the same IdP can consume…

more

it and get linked to the victim's local account.

CWE(s)
CWE-639

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1098 Account Manipulation Persistence
Adversaries may manipulate accounts to maintain and/or elevate access to victim systems.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Why these techniques?

CWE-639 IDOR in Keycloak IdP account linking directly enables unauthorized account manipulation (T1098) via exploitation of a public-facing auth service (T1190).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

Affected Assets

redhat
build of keycloak
all versions

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

AC-24 Access Control Decisions
addresses: CWE-639

Per-request decision making makes it harder to bypass authorization using user-controlled keys without proper validation in the decision process.

AC-3 Access Enforcement
addresses: CWE-639

Consistent enforcement of approved authorizations makes bypassing via user-controlled keys ineffective.

References