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No exploitation reportedFix available

CVE-2026-77368

SeaweedFS: Authenticated Cross-Prefix IDOR in Filer TUS Handler Enables Arbitrary Write to Tenant-Forbidden Paths

No exploitation reported by the sources we read.

  • Published2026-08-26
  • Fixed in4.40.0
  • WeaknessCWE-639

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

SeaweedFS is a distributed storage system for files and blobs. In version 4.39, the filer's TUS resumable-upload handler checks JWT allowed_prefixes scoping only when a session is created, letting a low-privilege tenant hijack another tenant's upload session to write content to filer paths their own token forbids. The HEAD, PATCH, and DELETE verbs that act on an existing session by its id never verify that the session's stored target path falls within the caller's allowed prefixes, so a tenant who obtains another upload's session identifier can PATCH attacker bytes into it and, on completion, have the file land at the victim's out-of-scope path. The same token can also DELETE other tenants' sessions and HEAD them to read upload progress and size, defeating the JWT prefix isolation. This vulnerability only affects deployments that configure filer JWT signing and have TUS uploads enabled. This issue is fixed in version 4.40.

Timeline

dates in UTC
  1. 2026-08-2622:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-30 03:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-77368?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-77368?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

OSV
seaweedfs
BranchAffectedFixed in
4.x≥ 4.39.0, < 4.40.04.40.0

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update seaweedfs to 4.40.0

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVE recordread 2026-10-23
  • CISA-ADPSSVC decisionnone2026-08-27
  • OpenCVESSVC decisionnone—
  • CNACVSS 3.17.6read 2026-10-23
  • CNAweakness (CWE)CWE-639read 2026-10-23
  • FIRST EPSSEPSS score0.4 %2026-10-29
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:L
Published
2026-08-26
Last Modified
2026-09-09
NVD status
Deferred

Frequently asked questions

What is CVE-2026-77368?

SeaweedFS is a distributed storage system for files and blobs. In version 4.39, the filer's TUS resumable-upload handler checks JWT allowed_prefixes scoping only when a session is created, letting a low-privilege tenant hijack another tenant's upload session to write content to filer paths their own token forbids. The HEAD, PATCH, and DELETE verbs that act on an existing session by its id never verify that the session's stored target path falls within the caller's allowed prefixes, so a tenant who obtains another upload's session identifier can PATCH attacker bytes into it and, on completion, have the file land at the victim's out-of-scope path. The same token can also DELETE other tenants' sessions and HEAD them to read upload progress and size, defeating the JWT prefix isolation. This vulnerability only affects deployments that configure filer JWT signing and have TUS uploads enabled. This issue is fixed in version 4.40.

Is CVE-2026-77368 actively exploited?

Active exploitation of CVE-2026-77368 has not been confirmed. Its EPSS score was 0.4% on 2026-10-29, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-77368?

CVE-2026-77368 has a CVSS v3 base score of 7.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:L.

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