How severe is CVE-2026-72921?

CVE-2026-72921 has a CVSS score of 8.1/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-72921?

CVE-2026-72921 affects the following packages: github.com/seaweedfs/seaweedfs (Go). Ecosystems affected: Go.

How do I fix CVE-2026-72921?

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.

How do I detect CVE-2026-72921 in my Go dependencies?

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.

How do I mitigate CVE-2026-72921 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-72921 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-72921 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-72921?

CVE-2026-72921 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 37th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-72921?

CVE-2026-72921 is classified as CWE-863 (CWE-863). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-72921 published, and has it been updated?

CVE-2026-72921 was published on August 11, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

HIGH severity

CVE-2026-72921 — seaweedfs

HIGHFix: seaweedfs/seaweedfs@05ed5c9

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

Also known asBIT-seaweedfs-2026-72921GHSA-gv5w-hfx8-8cwqGO-2026-6361

Published

Aug 11, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs37th percentile — riskier than 37% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐹github.com/seaweedfs/seaweedfs

Real-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 (JWT allowed_prefixes authorization 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

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/seaweedfs/seaweedfs`	all versions	0.0.0-20260512171048-05ed5c9ae8a2`go get github.com/seaweedfs/seaweedfs@v0.0.0-20260512171048-05ed5c9ae8a2`

Detection & mitigation playbook

Open-source dependency

Detect
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
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### 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