CVE-2026-82426: Apache Storm Nimbus: Arbitrary File Read on Nimbus via Unvalidated Uploaded Jar Location
Description
Nimbus accepted the uploadedJarLocation argument of submitTopology / submitTopologyWithOpts as a server-side path and opened it directly, without checking that it referred to a file the caller had actually uploaded. The intended flow is that a client first calls beginFileUpload, which returns a path inside the Nimbus inbox, and uploads the jar in chunks to that location; nothing bound submission to that flow, and the uploaders map populated by beginFileUpload was never consulted at submit time.
An authenticated user with topology submission rights could therefore submit any path readable by the Nimbus daemon user as their topology jar. Nimbus copied the file into the topology's jar blob, and the blob ACL grants the submitting subject read access, so the contents could then be retrieved with the ordinary blob download RPCs. Candidate targets include the Nimbus Kerberos keytab, Thrift and UI TLS private keys, and storm.yaml with the ZooKeeper authentication payload. Possession of the Nimbus keytab turns an ordinary tenant into a cluster administrator.
In a deployment configured as the documentation recommends, submission is available to every authenticated principal when nimbus.users is unset, so no elevated privilege is required.
Mitigation
Upgrade to 3.1.0, where the submitted location is canonicalised and must resolve inside the Nimbus inbox.
Users who cannot upgrade immediately should restrict topology submission to trusted principals via nimbus.users or nimbus.groups, and should treat any file readable by the Nimbus daemon user as potentially exposed to submitters: rotate the Nimbus keytab and any TLS private keys or ZooKeeper credentials reachable from that account. Local mode is unaffected.
Credit
Independently reported to the Apache Storm PMC by n0mi1k, with a proof of concept.
Also found by the ASF 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 3.1.0 - Configuration
If you cannot upgrade to 3.1.0 immediately, restrict topology submission to trusted principals by configuring nimbus.users (when unset, submission is available to every authenticated principal with topology submission rights).
Apache Storm Nimbus nimbus.users = restrict topology submission to trusted principals - Configuration
If you cannot upgrade to 3.1.0 immediately, restrict topology submission to trusted principals by configuring nimbus.groups.
Apache Storm Nimbus nimbus.groups = restrict topology submission to trusted principals - Compensating control
Treat any file readable by the Nimbus daemon user as potentially uploaded if the system cannot be upgraded yet.
- Operational
Rotate the Nimbus keytab and any TLS private keys or ZooKeeper private keys, and rotate storm.yaml with the ZooKeeper authentication payload, since an attacker could read files accessible to the Nimbus daemon user via this flaw.
Event History
Frequently Asked Questions
What access does an attacker need to exploit this issue?
The attacker must be authenticated and have topology submission rights. They do not need to use the intended upload process, because submission was not bound to a location returned by beginFileUpload.
What files could be exposed?
Any file readable by the Nimbus daemon user could be submitted as a topology jar. The described candidate targets include the Nimbus Kerberos keytab, Thrift and UI TLS private keys, and storm.yaml containing the ZooKeeper authentication payload.
Can this lead to cluster-level privilege escalation?
Yes. The description states that possession of the Nimbus Kerberos keytab can turn an ordinary tenant into a cluster administrator. The submitted file is copied into a blob whose ACL grants the submitting subject read access, allowing retrieval through normal blob download RPCs.