CVE-2025-27399 Information

Description

Mastodon is a self-hosted federated microblogging platform. In versions prior to 4.1.23 4.2.16 and 4.3.4 when the visibility for domain blocks/reasons is set to �sers\ (localized English string: \To logged-in users) users that are not yet approved can view the block reasons. Instance admins that do not want their domain blocks to be public are impacted. Versions 4.1.23 4.2.16 and 4.3.4 fix the issue.

Reference

https://github.com/mastodon/mastodon/blob/93f0427b8a84faf68d5d02cdf9a26f98fae16f2b/app/controllers/api/v1/instances/domain_blocks_controller.rb#L33-L35 https://github.com/mastodon/mastodon/blob/93f0427b8a84faf68d5d02cdf9a26f98fae16f2b/app/controllers/api/v1/instances/domain_blocks_controller.rb#L49-L51 https://github.com/mastodon/mastodon/commit/6b519cfefa93a923b19d0f20c292c7185f8fd5f5 https://github.com/mastodon/mastodon/security/advisories/GHSA-94h4-fj37-c825