Advisory [CVE-2026-82431] Apache Storm: Description `SimpleACLAuthorizer` evaluated the user-level command set by returning early when `nimbus.users` was empty, before `nimbus.groups` was considered
This security Apache Software Foundation advisory covers CVE-2026-82431 affecting Apache Storm.
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Summary
`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 is unchanged.
Affected product named by the advisory: Apache Storm.
- Apache Storm Client 3.0.0 before 3.1.0
Official advisory · medium-confidence parse· fetched 3 hours ago·verify at source
- 3.1.0
Official advisory · medium-confidence parse· fetched 3 hours ago·verify at source
Mitigation checklist
- 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.
Official advisory · medium-confidence parse· fetched 3 hours ago·verify at source
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