Executive Summary

CVE-2026-24901 is an Insecure Direct Object Reference (IDOR) vulnerability in Outline versions prior to 1.4.0, specifically in the document restoration logic.

This flaw allows any team member, even with low privileges, to unauthorizedly restore, view, and take ownership of deleted private drafts belonging to other users, including administrators.

The vulnerability occurs because the system does not properly verify if the user restoring a deleted draft is the original owner or has explicit permission, allowing attackers to bypass ownership validation.

• An attacker who knows the UUID of a deleted draft can access its content and restore it under their own ownership.
• The attacker can then publish the draft and lock the original owner out of their own content.

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Impact Analysis

This vulnerability can have several serious impacts:

• Unauthorized disclosure of sensitive private draft content to unauthorized team members.
• Theft of ownership of deleted drafts, allowing attackers to control and publish content they do not own.
• Denial of service for the original owner, who loses access to their own deleted drafts permanently.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by monitoring API requests to the `/api/documents.restore` endpoint, especially POST requests that attempt to restore deleted drafts. Suspicious activity includes restoration requests where the requester is not the original owner of the draft.'}, {'type': 'paragraph', 'content': 'To detect exploitation attempts, you can look for POST requests with parameters specifying draft IDs (UUIDs) and collection IDs that do not belong to the requester.'}, {'type': 'paragraph', 'content': 'Suggested commands to help detect this on a system running Outline might include:'}, {'type': 'list_item', 'content': 'Use network traffic monitoring tools (e.g., tcpdump, Wireshark) to filter HTTP POST requests to `/api/documents.restore`.'}, {'type': 'list_item', 'content': "Example tcpdump command: `tcpdump -A -s 0 'tcp port 80 or tcp port 443' | grep '/api/documents.restore'`"}, {'type': 'list_item', 'content': 'Check application logs for restoration events and verify if the user restoring the draft is the original owner.'}, {'type': 'list_item', 'content': 'Use API request logging or auditing features to track which user IDs are performing restore operations and on which draft UUIDs.'}] [1]

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Mitigation Strategies

The immediate mitigation step is to upgrade Outline to version 1.4.0 or later, where this vulnerability is fixed.

Until the upgrade can be performed, restrict team membership to trusted users only, as the vulnerability requires team membership to exploit.

Additionally, monitor and audit restore operations to detect unauthorized restoration attempts.

If possible, temporarily disable or restrict access to the `/api/documents.restore` endpoint to prevent unauthorized restores.

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