Auth bypass in Bookwyrm-Social Bookwyrm
CVE-2026-86112
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.
Vulnerability class: IDOR (Insecure Direct Object Reference)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (21.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 22nd percentile — 21.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
Weakness classification (CWE)
References
- github.com/bookwyrm-social/bookwyrm (product)
- Favorite/Unfavorite fetch by id with no visibility check (technical-description)
- Researcher write-up: finding 2 (technical-description)
- VulnCheck Advisory: BookWyrm through 0.9.1 Missing Authorization on the Favorite and Unfavorite Endpoints (third-party-advisory)
Frequently asked questions
- What is CVE-2026-86112?
- CVE-2026-86112 is a medium-severity vulnerability in Bookwyrm-Social Bookwyrm, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 5.4/10. Published 2026-09-05.
- How severe is CVE-2026-86112?
- Medium severity. CVSS v3 base score is 5.4 out of 10.