CVE-2019-25585: Deluge-torrent Deluge DOS Vulnerability

CVE-2019-25585 Overview

CVE-2019-25585 is a denial of service vulnerability affecting Deluge 1.3.15, a popular open-source BitTorrent client. The vulnerability allows local attackers to crash the application by supplying an excessively long string in the Webseeds field during torrent creation. By pasting a buffer of approximately 5000 bytes into the Webseeds field, an attacker can trigger an application crash, disrupting normal operations for legitimate users.

Critical Impact

Local attackers can cause complete application denial of service by exploiting improper input validation in the Webseeds field, leading to application crashes and service disruption.

Affected Products

• Deluge 1.3.15 (Windows)
• deluge-torrent deluge 1.3.15

Discovery Timeline

• 2026-03-22 - CVE CVE-2019-25585 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2019-25585

Vulnerability Analysis

This denial of service vulnerability exists in the Deluge BitTorrent client's handling of user input within the Webseeds field. The application fails to properly validate the length of strings entered into this field during the torrent creation process. When a user or attacker supplies an excessively long string (approximately 5000 bytes), the application is unable to handle the oversized input correctly, resulting in an application crash.

The vulnerability is classified under CWE-1260, which relates to improper handling of inconsistent special elements. This type of vulnerability occurs when software does not properly handle or incorrectly handles input that contains inconsistent or malformed data that doesn't match expected patterns or boundaries.

Root Cause

The root cause of this vulnerability is insufficient input validation in the Webseeds field handler. The application does not enforce appropriate length limits on user-supplied input, allowing excessively large strings to be processed. This improper boundary checking leads to resource exhaustion or buffer handling issues when the application attempts to process the oversized input, ultimately causing the application to crash.

Attack Vector

The attack vector is local, requiring the attacker to have direct access to the Deluge application interface. The exploitation process involves:

1. Opening the Deluge application and navigating to the torrent creation interface
2. Locating the Webseeds input field
3. Pasting or entering a buffer of approximately 5000 bytes or more
4. The application fails to properly validate the input length
5. The application crashes due to improper handling of the oversized string

This vulnerability does not require authentication and has no user interaction requirements beyond the attacker themselves initiating the malicious input. While the attack vector is local, it can still cause significant disruption in environments where Deluge is used for legitimate file sharing operations.

Detection Methods for CVE-2019-25585

Indicators of Compromise

• Unexpected Deluge application crashes, particularly during torrent creation operations
• Application log entries showing failures related to Webseed field processing
• Crash dump files indicating memory handling issues in the torrent creation component

Detection Strategies

• Monitor for repeated application crashes of deluge.exe or the Deluge process
• Implement application crash monitoring to detect patterns of DoS attempts
• Review system event logs for Deluge application failure events
• Deploy endpoint detection rules to identify abnormal application termination patterns

Monitoring Recommendations

• Enable verbose logging in Deluge to capture detailed error information
• Set up automated alerts for Deluge process crashes in enterprise environments
• Monitor system stability metrics on machines running Deluge
• Consider implementing application whitelisting to control who can interact with the Deluge client

How to Mitigate CVE-2019-25585

Immediate Actions Required

• Upgrade Deluge to a version newer than 1.3.15 where input validation has been improved
• Restrict local access to systems running vulnerable Deluge installations
• Consider temporarily disabling torrent creation functionality if updates cannot be immediately applied
• Review and limit user permissions on systems with Deluge installed

Patch Information

Users should upgrade to a newer version of Deluge beyond 1.3.15. Consult the Deluge Development Repository for the latest stable release and security updates. The vulnerability was documented with a public exploit available on Exploit-DB #46884, making prompt patching essential.

For additional technical details, refer to the Vulncheck Deluge DoS Advisory.

Workarounds

• Restrict local access to Deluge installations to trusted users only
• Implement application-level access controls to limit who can create torrents
• Use endpoint protection solutions to monitor for and prevent abnormal application behavior
• Consider running Deluge in a sandboxed environment to contain potential crashes