CVE-2026-0871 is a medium-severity (CVSS 4.9) CWE-266 vulnerability in org.keycloak:keycloak-server-spi-private. A fix is available for org.keycloak:keycloak-server-spi-private — see the affected versions and patch details below.
Org.keycloak/keycloak-services: keycloak: unauthorized modification of unmanaged user attributes by administrators
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-0871.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-0871 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.keycloak:keycloak-server-spi-privateReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
A flaw was found in Keycloak. An administrator with manage-users permission can bypass the "Only administrators can view" setting for unmanaged attributes, allowing them to modify these attributes. This improper access control can lead to unauthorized changes to user profiles, even when the system is configured to restrict such modifications.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.keycloak:keycloak-server-spi-private | all versions | 26.5.2org.keycloak:keycloak-server-spi-private:26.5.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.keycloak:keycloak-server-spi-private, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.keycloak:keycloak-server-spi-private to 26.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-0871 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-0871 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-0871. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is rated Moderate for Red Hat. An administrator with `manage-users` permission can modify unmanaged user attributes in Keycloak, even when the "Only administrators can view" setting is enabled. This bypass requires the realm to be configured with unmanaged attributes set to "Only administrators can…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat build of Keycloak 26.4 | rhbk/keycloak-operator-bundle:26.4.9-1 | RHSA-2026:2366 |
| Red Hat build of Keycloak 26.4.9 | rhbk/keycloak-rhel9 | RHSA-2026:2365 |
Frequently Asked Questions
Is CVE-2026-0871 in your dependencies?
O3 Security finds CVE-2026-0871 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.