continuwuity up to 0.5.0 /leave origin_server_ts content confused deputy

Summaryinfo

A vulnerability was found in continuwuity up to 0.5.0 and classified as critical. Affected by this issue is the function origin_server_ts of the file /leave. The manipulation of the argument content results in confused deputy. This vulnerability is reported as CVE-2026-24471. The attack can be launched remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in continuwuity up to 0.5.0. Affected is the function origin_server_ts of the file /leave. The manipulation of the argument content with an unknown input leads to a confused deputy vulnerability. CWE is classifying the issue as CWE-441. The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

continuwuity is a Matrix homeserver written in Rust. This vulnerability allows an attacker with a malicious remote server to cause the local server to sign an arbitrary event upon user interaction. Upon a user account leaving a room (rejecting an invite), joining a room or knocking on a room, the victim server may ask a remote server for assistance. If the victim asks the attacker server for assistance the attacker is able to provide an arbitrary event, which the victim will sign and return to the attacker. For the /leave endpoint, this works for any event with a supported room version, where the origin and origin_server_ts is set by the victim. For the /join endpoint, an additionally victim-set content field in the format of a join membership is needed. For the /knock endpoint, an additional victim-set content field in the format of a knock membership and a room version not between 1 and 6 is needed. This was exploited as a part of a larger chain against the continuwuity.org homeserver. This vulnerability affects all Conduit-derived servers. This vulnerability is fixed in Continuwuity 0.5.1, Conduit 0.10.11, Grapevine 0aae932b, and Tuwunel 1.4.9.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-24471 since 01/23/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

Upgrading to version 0.5.1 eliminates this vulnerability. Applying the patch 12aecf809172205436c852a1eaf268c1a2c3a900 is able to eliminate this problem. The bugfix is ready for download at forgejo.ellis.link. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• continuwuity

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5.0

Website

• Product: https://github.com/continuwuity/continuwuity/

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