CVE-2026-82431
CVE-2026-82431 is a CWE-863 vulnerability. O3 Security confirms whether CVE-2026-82431 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
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…
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- 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-2026-82431.
Description
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 additionally populate nimbus.users with the intended
principals, since a non-empty user list causes the group list to be evaluated on affected versions.
Operators should review Nimbus access logs for operations by principals outside the intended groups.
Note that after upgrading, a cluster configured with nimbus.groups alone becomes restrictive for the first
time. This includes NimbusClient, which calls getLeader on every connection, so clients outside the
configured groups will begin to be refused.
Credit
The ASF -- found using Claude agents to study the security of open-source projects, validated and reported by Apache Storm.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-82431 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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 pinpoints whether CVE-2026-82431 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-82431. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-82431 in your dependencies?
O3 detects CVE-2026-82431 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.