EUVD-2026-66758Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:L
PR:L confirmed by requirement for a valid JWT token; I:H reflects arbitrary cross-tenant file writes; C:L for session metadata exposure via HEAD.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:L
Lifecycle Timeline
4DescriptionCVE.org
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.
AnalysisAI
SeaweedFS 4.39's TUS resumable-upload handler fails to re-validate JWT prefix scoping on HEAD, PATCH, and DELETE operations against existing sessions, enabling a low-privilege authenticated tenant to hijack cross-tenant upload sessions. An attacker holding a valid but restricted JWT token can PATCH arbitrary content into another tenant's in-progress upload by reusing the victim's session ID, causing the completed file to land at a filesystem path the attacker's token explicitly forbids. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires all three of the following conditions to be simultaneously true: (1) the SeaweedFS filer must have JWT signing configured and active (filerGuard enabled); (2) TUS resumable uploads must be enabled on the filer (the /.tus route must be accessible); and (3) the deployment must use prefix-restricted JWT tokens - specifically tokens with non-empty AllowedPrefixes fields - for multi-tenancy isolation. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:L, score 7.6) accurately reflects the attack profile: network-accessible, low complexity, requiring only a low-privilege JWT token. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker authenticated with a JWT token scoped to /buckets/attacker/ observes a co-tenant's in-progress TUS upload session ID - obtainable via shared infrastructure logs, network interception, or insider knowledge - targeting /buckets/secret/sensitive.bin. The attacker sends PATCH requests to the victim's session ID using their own valid restricted token, injecting malicious content; upon TUS upload completion, the tampered file lands at /buckets/secret/sensitive.bin, a path the attacker's token forbids, fully bypassing the AllowedPrefixes isolation. … |
| Remediation | Upgrade to SeaweedFS version 4.40, which contains the complete fix across commits ce82e3a057080162a9fba11889157d2255815f71 and fa549e9c83b7799d512157d728f52052912831af available in the project repository. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all SeaweedFS 4.39 deployments and confirm if they operate in multi-tenant mode with JWT authentication enabled. …
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External POC / Exploit Code
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