CVE-2026-54741
Lemmy: Blocked users can edit private messages sent before the block
- State
- Published
- Severity
- 5.3 Medium
- Published
- Aug 19, 2026
- Updated
- Aug 20, 2026
- Reserved
- Jun 15, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.3 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N | GitHub_M |
Weaknesses
- CWE-862 Missing Authorization
Affected Products
| Product | Versions |
|---|---|
lemmyLemmyNet |
|
References
- https://github.com/LemmyNet/lemmy/security/advisories/GHSA-46g9-847m-qf8r
- https://github.com/LemmyNet/lemmy/pull/6472
- https://github.com/LemmyNet/lemmy/pull/6476
- https://github.com/LemmyNet/lemmy/commit/051b317c9d14b91972bb372c67f319d6900beb93
- https://github.com/LemmyNet/lemmy/commit/2d169d630b86b9351e4b1dca451214b741f46150
- https://github.com/LemmyNet/lemmy/releases/tag/0.19.19
- https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18
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