Vulnerability Snapshot
CVE-2026-82431 is rated CRITICAL — exploitation is trivial or already observed in the wild and impact is severe. Patch immediately, not on the next maintenance window.
Executive Summary
Description
SimpleACLAuthorizer evaluated the user-level command set by returning early when nimbus.users was empty,
before nimbus.groups was considered. An operator who restricted cluster access by group alone, leaving
nimbus.users unset, therefore received no restriction at all: every authenticated principal was permitted
every user-level operation, including submitTopology, beginFileUpload and getNimbusConf.
docs/SECURITY.md presents nimbus.groups as a supported way to lock down a cluster, so a deployment
following the documentation could believe it was restricted while it was not. The failure is silent; nothing
in the logs or the configuration indicates that the group list is being ignored.
Both lists left empty continues to mean that no restriction is configured, which is the shipped default and
is unchanged.
Mitigation
Upgrade to 3.1.0, where nimbus.groups is evaluated whether or not nimbus.users is set.
Users who cannot upgrade immediately should addi
Why It Matters
CVE-2026-82431 is rated CRITICAL severity, requiring immediate attention from security teams.
CVSS Base Score: 9.8/10
🛡️What Defenders Should Check
Use Vulnios to continuously monitor your exposure to CVE-2026-82431 and similar vulnerabilities.
References & Sources
How Vulnios Detects This
Vulnios scans for this vulnerability using Trivy and Grype for SBOM-based CVE matching and Vulnios CVE feed continuous monitoring against your asset inventory. Run a scan against your environment to see whether you are exposed; findings are linked back to the original CVE record so triage starts with the patch path already known.
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Sources
Related Threat Alerts
Frequently Asked Questions
What is CVE-2026-82431?
CVE-2026-82431 is a critical-severity vulnerability tracked under the Common Vulnerabilities and Exposures program. Description
SimpleACLAuthorizer evaluated the user-level command set by returning early when nimbus.users was empty,
before nimbus.groups was considered. An operator who restricted cluster acce
Am I affected?
Affected technology is listed in the Affected Products section above. If your asset inventory contains any of them, assume in-scope until you can prove otherwise.
How urgent is the response?
Critical: do not wait for your normal patch cycle. Verify exposure today, apply the vendor patch immediately, and add detection rules for any post-exploit indicators.
How do I remediate?
Apply the vendor patch listed in the upstream advisory linked under Sources. If the patch is not yet available, follow the vendor-supplied workaround (often a config flag or feature disable) and add detections for the published exploit pattern in your SIEM. Re-scan after the patch lands to confirm the finding clears.
Where can I track exploitation activity?
Watch CISA's Known Exploited Vulnerabilities catalog for CVE-2026-82431. Cross-reference with public exploit databases and your own SIEM/IDS for indicator-of-compromise patterns. Vulnios tracks KEV status automatically and surfaces it on the asset findings view.
How does Vulnios help with this?
Vulnios continuously cross-references your asset inventory against the live CVE feed (NVD, vendor advisories, CISA KEV, and curated OSINT). When a new CVE matches your environment, you get a prioritized finding with the severity, KEV status, exploit-prediction (EPSS), and a direct path to the vendor patch. You can start a free scan from the homepage.
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