CVE-2026-72921 is a high-severity (CVSS 8.1) CWE-863 vulnerability in github.com/seaweedfs/seaweedfs. A fix is available for github.com/seaweedfs/seaweedfs — see the affected versions and patch details below.
SeaweedFS: Filer JWT allowed_prefixes literal prefix match allows cross-tenant access to sibling paths
Exploitation Status
No confirmed exploitation observed yet
- 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-2026-72921.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-72921 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/seaweedfs/seaweedfsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
When a filer JWT restricts a token to a set of path prefixes via allowed_prefixes, the authorization check used a literal byte-prefix match (strings.HasPrefix). A token scoped to /tenant1 therefore also authorized requests to sibling paths such as /tenant1234, /tenant1-old, and /tenant1backup.
In a multi-tenant deployment this lets the holder of one tenant's token access another tenant's data. Because allowed_prefixes gates both read and write tokens, the impact covers cross-tenant reads and writes. A valid scoped token is required, so this is an authorization bypass rather than a fully unauthenticated flaw.
Affected component
weed/server/filer_server_handlers.go(JWTallowed_prefixesauthorization check)
Patches
Fixed in 4.24. The check now matches on /-separated path components after path.Clean normalisation, so /tenant1 authorizes only /tenant1 and its descendants — not /tenant1234 or other sibling paths.
Workarounds
Where feasible, choose prefix names that are not string-prefixes of one another (e.g. keep a trailing separator convention). Upgrade to 4.24.
References
- Reported by Kadir Arslan (https://github.com/KadirArslan)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/seaweedfs/seaweedfs | all versions | 0.0.0-20260512171048-05ed5c9ae8a2go get github.com/seaweedfs/seaweedfs@v0.0.0-20260512171048-05ed5c9ae8a2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/seaweedfs/seaweedfs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/seaweedfs/seaweedfs to 0.0.0-20260512171048-05ed5c9ae8a2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-72921 is resolved across your whole dependency graph.
Workarounds
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-72921 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-72921. 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-2026-72921 in your dependencies?
O3 Security finds CVE-2026-72921 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.