Vulnerability · Published Sep 5, 2026 · Assigned by VulnCheck

CVE-2026-86112BookWyrm through 0.9.1 Missing Authorization on the Favorite and Unfavorite Endpoints

Medium 5.4

In plain English

A medium-severity authorization bypass via user-controlled key in bookwyrm from bookwyrm-social. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities).

Severity (CVSS 3.1)5.4Medium

Exploit odds (30 days)0.3%top 76.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
bookwyrm-social	bookwyrm	0 – through 0.9.1

Weakness: CWE-639 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

References

Researcher write-up: finding 2 technical-description
Favorite/Unfavorite fetch by id with no visibility check technical-description
https://github.com/bookwyrm-social/bookwyrm product
VulnCheck Advisory: BookWyrm through 0.9.1 Missing Authorization on the Favorite and Unfavorite Endpoints third-party-advisory