LemmyNet Lemmy up to 0.19.15 Query Parameter /api/v4/image/ file_type server-side request forgery

Summaryinfo

A vulnerability was found in LemmyNet Lemmy up to 0.19.15. It has been declared as critical. Impacted is an unknown function of the file /api/v4/image/ of the component Query Parameter Handler. The manipulation of the argument file_type results in server-side request forgery. This vulnerability is known as CVE-2026-29178. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in LemmyNet Lemmy up to 0.19.15. It has been classified as critical. Affected is some unknown processing of the file /api/v4/image/ of the component Query Parameter Handler. The manipulation of the argument file_type with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Lemmy, a link aggregator and forum for the fediverse, is vulnerable to server-side request forgery via a dependency on activitypub_federation, a framework for ActivityPub federation in Rust. Prior to version 0.19.16, the GET /api/v4/image/{filename} endpoint is vulnerable to unauthenticated SSRF through parameter injection in the file_type query parameter. An attacker can inject arbitrary query parameters into the internal request to pict-rs, including the proxy parameter which causes pict-rs to fetch arbitrary URLs. This issue has been patched in version 0.19.16.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-29178 since 03/04/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit.

Upgrading to version 0.19.16 eliminates this vulnerability. Applying the patch f47a03f56d1797bceab5f34b6f624c91cecd5871 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• LemmyNet

Name

• Lemmy

Version

• 0.19.0
• 0.19.1
• 0.19.2
• 0.19.3
• 0.19.4
• 0.19.5
• 0.19.6
• 0.19.7
• 0.19.8
• 0.19.9
• 0.19.10
• 0.19.11
• 0.19.12
• 0.19.13
• 0.19.14
• 0.19.15

License

• open-source

Website

• Product: https://github.com/LemmyNet/lemmy/

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