Bug 2484166 (CVE-2026-45283)

Summary: CVE-2026-45283 nextcloud-server: Nextcloud Server: Unauthorized file modification and denial of service via improper WebDAV handling
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Nextcloud Server. An authenticated user could exploit this vulnerability to lock or unlock files belonging to other users by manipulating WebDAV (Web Distributed Authoring and Versioning) paths. This issue also led to the disclosure of lock tokens in error responses, potentially allowing attackers to remove locks set by legitimate users. The consequences include unauthorized file modification and a potential denial of service.
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Bug Depends On: 2484170, 2484172    
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Description OSIDB Bzimport 2026-06-02 21:06:41 UTC
Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.2, and 33.0.0 to before 33.0.1, the files_lock app did not properly validate the ownership of files when processing DAV lock and unlock requests. An authenticated user could lock or unlock files belonging to other users by targeting their absolute WebDAV paths. Additionally, lock tokens were disclosed to unauthorized callers in error responses, allowing attackers to remove token-based locks placed by other users' client applications. It is recommended that the Nextcloud Server is upgraded to 32.0.2 or 33.0.1. It is recommended that the Nextcloud Enterprise Server is upgraded to 31.0.14.4 or 32.0.2 or 33.0.1