CVE-2026-82427: Apache Storm Nimbus: Path Traversal as the Supervisor User via Unsanitised Blobstore Map Local Name
Description
A topology's topology.blobstore.map lets the submitter choose a local name for each blob that the supervisor localises. That name was used to build a path under the topology's working directory without normalisation, in both AsyncLocalizer and Container.createBlobstoreLinks, and the symlink helper force-deletes whatever already exists at the target before creating the link.
A submitter could therefore use ../ segments to direct that delete-and-symlink operation at an arbitrary path, as the supervisor user, on every node the topology is scheduled onto. The consequences include recursive deletion of supervisor-owned content and planting a symlink that causes a subsequent worker launch to execute attacker-chosen code as another tenant's operating-system user, which defeats the isolation that supervisor.run.worker.as.user is intended to provide.
Mitigation
Upgrade to 3.1.0, where the resolved target must lie inside the expected root at both call sites.
Users who cannot upgrade immediately should restrict topology submission to trusted principals, and may reject submissions whose topology.blobstore.map entries contain path separators or .. segments before they reach Nimbus.
Credit
The ASF -- found using Claude agents to study the security of open-source projects, validated and reported by Apache Storm.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Apache Storm Nimbusto a version that resolves this vulnerability.Fixed in 3.1.0Patch CVE-2026-82427 - Compensating control
For environments that cannot upgrade immediately, restrict topology submission to trusted principals.
- Compensating control
Before supervisor localises topologies, ensure entries in `topology.blobstore.map` are rejected if they contain path separators or `..` segments.
Event History
Frequently Asked Questions
Who can exploit this issue in practice?
A topology submitter can exploit it by choosing malicious local names in topology.blobstore.map. Impact occurs on every node onto which that topology is scheduled, with filesystem operations performed as the supervisor user.
Does exploitation require a particular worker-user isolation setting?
The path traversal and supervisor-user delete-and-symlink operation stem from the unsanitised blobstore map local name. When supervisor.run.worker.as.user is used, the planted symlink can cause a later worker launch to execute attacker-chosen code as another tenant's operating-system user, defeating that intended isolation.
What should we do if we cannot upgrade immediately?
Restrict topology submission to trusted principals. As an additional interim control, reject submissions with topology.blobstore.map entries containing path separators or '..' segments.
How can we remediate the vulnerability?
Upgrade to Apache Storm version 3.1.0. That version requires the resolved target to remain inside the expected root at both affected call sites.