Overview
CVE-2025-66515 is a low-severity vulnerability discovered in the Nextcloud Approval app. This flaw allows an authenticated user listed as a requester in a workflow to inappropriately set another user’s file into the “pending approval” state, even without having access to the file itself. This is achieved by exploiting the numeric file ID within the Approval app.
The vulnerability affects versions prior to 1.3.1 and 2.5.0 of the Nextcloud Approval app. Users are strongly encouraged to update to the patched versions to mitigate the risk.
Technical Details
The vulnerability stems from insufficient access control checks when a user triggers the “pending approval” state for a file within a workflow. The Nextcloud Approval app, prior to the patched versions, utilized the numeric file ID without proper validation of the requester’s access permissions to the target file. As a result, an authenticated user who is part of a workflow could manipulate the workflow by referencing the numeric ID of a file they wouldn’t normally have access to, effectively placing it into the “pending approval” state for another user.
This bypass is possible because the app does not properly verify if the requester is authorized to initiate the approval process on the specified file based on file access permissions.
CVSS Analysis
- CVE ID: CVE-2025-66515
- Severity: LOW
- CVSS Score: 2.7
A CVSS score of 2.7 indicates a low-severity vulnerability. While the vulnerability could potentially disrupt workflows, it requires an authenticated user to exploit and does not directly lead to data breaches or system compromise. The CVSS vector likely reflects the low impact and exploitability given the authentication requirement.
Possible Impact
The exploitation of CVE-2025-66515 could lead to the following potential impacts:
- Workflow Disruption: Unauthorized initiation of approval requests can disrupt normal workflows and potentially delay access to files.
- Denial of Service (Minor): Repeated manipulation of the approval status of files could potentially lead to a minor denial of service for legitimate users awaiting file approvals.
- Information Disclosure (Limited): While not a direct disclosure vulnerability, an attacker might be able to infer the existence of specific files by attempting to trigger approval requests using file IDs.
Mitigation and Patch Steps
To mitigate the risk associated with CVE-2025-66515, users of the Nextcloud Approval app are strongly advised to upgrade to the following versions or later:
- Version 1.3.1
- Version 2.5.0
These versions contain the necessary security fixes to address the unauthorized workflow manipulation vulnerability. Updating the Approval app through the Nextcloud app store is the recommended approach.
