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CVE-2026-77611· NVD / CVE Program· CNA GitHub_M

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

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.

HighCVSS 7.1 · v3.1—No exploit Fix available
Published
Aug 26, 2026
Updated
Sep 9, 2026
EPSS
0.4% · 30th percentile
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Report tools

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Action score

28

Monitor

Low priority for now.

CVSS
28 / 40 · 7.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
7.1
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • seaweedfs seaweedfs

    • < 4.40affected

Same product

seaweedfs: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-72920SeaweedFS: Unauthenticated filer IAM gRPC service grants S3 administrative control
    39Monitor
  • CVE-2026-73080SeaweedFS: Unauthenticated SSRF with response read-back via VolumeServer.FetchAndWriteNeedle
    37Monitor
  • CVE-2026-77298SeaweedFS S3 OIDC Bearer authentication bypasses IAM role trust policy
    34Monitor
  • CVE-2026-77317SeaweedFS: SFTP path ACL literal prefix match permits cross-tenant file read and overwrite
    32Monitor
  • CVE-2026-72921SeaweedFS: Filer JWT allowed_prefixes literal prefix match allows cross-tenant access to sibling paths
    32Monitor
  • CVE-2026-54917SeaweedFS: Path traversal in the S3 and Iceberg REST gateways allows cross-bucket access
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
seaweedfs seaweedfs4.40 · descriptionVendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-772980 days apartSeaweedFS S3 OIDC Bearer authentication bypasses IAM role trust policy
    34Monitor
  • CVE-2026-773170 days apartSeaweedFS: SFTP path ACL literal prefix match permits cross-tenant file read and overwrite
    32Monitor
  • CVE-2026-7292115 days apartSeaweedFS: Filer JWT allowed_prefixes literal prefix match allows cross-tenant access to sibling paths
    32Monitor
  • CVE-2026-5587349 days apartSeaweedFS: Improper authorization in the S3Tables / Iceberg REST management API lets a low-privileged S3 user enumerate administrator-owned table buckets
    17Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
low · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
Low

Weakness class (CWE)

CWE-863 · Incorrect Authorization

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records