What’s Vulnerable › Vulnerabilities

CVE-2026-54741: Lemmy: Blocked users can edit private messages sent before the block

• Severity: medium (CVSS 5.3 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-19 · updated 2026-09-09
• Weakness: CWE-862

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.

Affected products

• LemmyNet lemmy: before 0.19.19; from 1.0.0-alpha.0, < 1.0.0-alpha.18

References

• https://github.com/LemmyNet/lemmy/commit/051b317c9d14b91972bb372c67f319d6900beb93
• https://github.com/LemmyNet/lemmy/commit/2d169d630b86b9351e4b1dca451214b741f46150
• https://github.com/LemmyNet/lemmy/pull/6472
• https://github.com/LemmyNet/lemmy/pull/6476
• https://github.com/LemmyNet/lemmy/releases/tag/0.19.19
• https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18
• https://github.com/LemmyNet/lemmy/security/advisories/GHSA-46g9-847m-qf8r
• https://github.com/LemmyNet/lemmy/security/advisories/GHSA-46g9-847m-qf8r

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