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.
