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Nextcloud Files Lock CVE-2026-82980

| EUVDEUVD-2026-82617 MEDIUM
Improper Authentication (CWE-287)
2026-09-18 hackerone GHSA-3vwx-p83m-w7p5
6.3
CVSS 3.0 · Vendor: hackerone
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Severity by source

Vendor (hackerone) PRIMARY
6.3 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
vuln.today AI
6.3 MEDIUM

Network WebDAV, low complexity, requires a valid low-privilege account (PR:L); lock-token disclosure is C:L, blocking victim writes is I:L/A:L, scope unchanged.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

Primary rating from Vendor (hackerone).

CVSS VectorVendor: hackerone

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
Low

Lifecycle Timeline

3
Metadata Corrected
Sep 18, 2026 - 02:40 vuln.today
tag: PHP added
Analysis Generated
Sep 18, 2026 - 02:01 vuln.today
CVE Published
Sep 18, 2026 - 01:26 cve.org
MEDIUM 6.3

DescriptionCVE.org

Any authenticated user can lock or unlock files they do not own by targeting absolute WebDAV paths of other users. The DAV plugin resolves files from the absolute request URI without verifying that the path segment matches the authenticated session user. This enables:

Cross-user manual locks : attacker locks a victim's files, blocking writes (PUT/MOVE/DELETE, editor saves). Lock-token disclosure: the app returns the lock token to unauthorized callers, enabling them to remove token-based locks (client locks) of other users.

AnalysisAI

Cross-user lock manipulation in the Nextcloud Files Lock (files_lock) app allows any authenticated user to lock or unlock files they do not own by supplying the absolute WebDAV path of another user's file, because the DAV plugin resolves the request URI without confirming that the path belongs to the session user. An attacker who can enumerate or guess a victim's path can block editor saves and PUT/MOVE/DELETE writes, and can also have the application hand back the victim's lock token, which enables removal of token-based client locks. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Execution
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Impact
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Vulnerability AssessmentAI

Exploitation Requires a valid authenticated account on the target Nextcloud instance (PR:L) and that the Files Lock (files_lock) app is enabled, exposing the WebDAV LOCK/UNLOCK endpoints. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a medium-severity, authenticated authorization flaw rather than a critical priority. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation No vendor-released patch was identified at time of analysis, so remediation depends on the compensating controls available in the input data. … Detailed patch versions, workarounds, and compensating controls in full report.

Threat intelligence, references, and detailed analysis are available after sign-in.

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CVE-2026-82980 vulnerability details – vuln.today

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