CVE-2026-86112

Description

BookWyrm through 0.9.1 fails to validate user visibility permissions in the Favorite and Unfavorite views, allowing authenticated attackers to favorite or unfavorite followers-only and direct statuses they cannot access. Attackers can POST to the favorite endpoint with a status ID to create unauthorized interactions, trigger ActivityPub broadcasts, and enumerate private status IDs through response differentiation.

References

• https://github.com/bookwyrm-social/bookwyrm
• https://github.com/bookwyrm-social/bookwyrm/blob/v0.9.1/bookwyrm/views/interaction.py
• https://github.com/geo-chen/oss/blob/main/bookwyrm.md#finding-2-authenticated-idor-in-favoriteunfavorite-allows-interaction-with-private-statuses
• https://www.vulncheck.com/advisories/bookwyrm-through-0.9.1-missing-authorization-on-the-favorite-and-unfavorite-endpoints