CVE-2026-54741
MediumCVSS 5.3Summary
Lemmy before versions 0.19.19 and 1.0.0-alpha.18 does not check the block list when editing private messages. A blocked sender can still edit old messages that the recipient can see, enabling post-block harassment.
Risk Assessment
A blocked user can continue sending unwanted content to the recipient, violating privacy and potentially leading to harassment.
Recommendation
Upgrade Lemmy to version 0.19.19 or 1.0.0-alpha.18, which include the fix.
Original NVD description (English source)
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.