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Public proof of conceptFix available

CVE-2026-77611

SeaweedFS: Authenticated S3 object-scope bypass in PutObjectAcl allows overwriting a different object with the same basename

A public proof of concept exists; no exploitation attested.

  • Published2026-08-26
  • Fixed in4.40.0
  • WeaknessCWE-863

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 versions prior to 4.40, an authenticated S3 principal with permissions scoped to a nested object key can overwrite a different object outside that scope by calling PutObjectAcl on the key it is allowed to access. The handler authorizes the request against the requested nested key but then writes the updated entry back to the bucket root rather than the key's actual parent directory, so an ACL change on allowed/protected.txt is instead applied to protected.txt at the bucket root. Because the update carries the full entry rather than only ACL metadata, an existing target object is overwritten with the content, metadata, owner information, and ACL of the scoped object, bypassing the object-level action scoping configured through the static S3 identity file. 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 09:37 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-2026-77611?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-77611?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
4.40< 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 decisionpoc2026-08-27
  • OpenCVESSVC decisionpoc—
  • CNACVSS 3.17.1read 2026-10-23
  • CNAweakness (CWE)CWE-863read 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:N/I:H/A:L
Published
2026-08-26
Last Modified
2026-09-09
NVD status
Deferred

Frequently asked questions

What is CVE-2026-77611?

SeaweedFS is a distributed storage system for files and blobs. In versions prior to 4.40, an authenticated S3 principal with permissions scoped to a nested object key can overwrite a different object outside that scope by calling PutObjectAcl on the key it is allowed to access. The handler authorizes the request against the requested nested key but then writes the updated entry back to the bucket root rather than the key's actual parent directory, so an ACL change on allowed/protected.txt is instead applied to protected.txt at the bucket root. Because the update carries the full entry rather than only ACL metadata, an existing target object is overwritten with the content, metadata, owner information, and ACL of the scoped object, bypassing the object-level action scoping configured through the static S3 identity file. This issue is fixed in version 4.40.

Is CVE-2026-77611 actively exploited?

A proof-of-concept exploit exists for CVE-2026-77611, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-77611?

CVE-2026-77611 has a CVSS v3 base score of 7.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L.

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