LemmyNet Lemmy up to 0.19.18/1.0.0-alpha.17 Private Message Edit update.rs edit_private_message access control

Summaryinfo

A vulnerability classified as problematic has been found in LemmyNet Lemmy up to 0.19.18/1.0.0-alpha.17. This impacts the function edit_private_message of the file crates/api/api_crud/src/private_message/update.rs of the component Private Message Edit. The manipulation leads to access control. This vulnerability is listed as CVE-2026-54741. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in LemmyNet Lemmy up to 0.19.18/1.0.0-alpha.17 and classified as problematic. This issue affects the function edit_private_message of the file crates/api/api_crud/src/private_message/update.rs of the component Private Message Edit. The manipulation with an unknown input leads to a access control vulnerability. Using CWE to declare the problem leads to CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Impacted is integrity. The summary by CVE is:

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, Lemmy blocks new private messages from a sender after the recipient blocks that sender, but the edit path skips the same block check. create_private_message checks the recipient's block list with PersonActions::read_block before inserting a message, while edit_private_message in crates/api/api_crud/src/private_message/update.rs only checks that the caller is orig_private_message.creator_id. The update then writes new content and returns the modified PrivateMessageView without consulting the recipient's block list, allowing a blocked sender to keep changing an old message that the recipient can still see and providing a post-block harassment path. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.18.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-54741 since 06/16/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1068 for this issue.

Upgrading to version 0.19.19 or 1.0.0-alpha.18 eliminates this vulnerability.

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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
• 0.19.16
• 0.19.17
• 0.19.18
• 1.0.0-alpha.0
• 1.0.0-alpha.1
• 1.0.0-alpha.2
• 1.0.0-alpha.3
• 1.0.0-alpha.4
• 1.0.0-alpha.5
• 1.0.0-alpha.6
• 1.0.0-alpha.7
• 1.0.0-alpha.8
• 1.0.0-alpha.9
• 1.0.0-alpha.10
• 1.0.0-alpha.11
• 1.0.0-alpha.12
• 1.0.0-alpha.13
• 1.0.0-alpha.14
• 1.0.0-alpha.15
• 1.0.0-alpha.16
• 1.0.0-alpha.17

Website

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

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