CVE-2026-67204

BookStack before 26.05.4 contains a broken access control vulnerability that allows authenticated API users with image-update or image-delete permissions to manipulate other users' avatars by exploiting missing content-type restrictions in the Image Gallery API endpoints. Attackers can supply a user avatar's ID to the API controller, which loads any image type without the web controller's gallery and drawio restrictions, and when the avatar's uploaded_to field matches a page ID accessible to the attacker, the authorization check passes allowing the attacker to rename, replace, or delete the target user's avatar without requiring user-management permission.

CVSS 4.0

5.3CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

CVSS 3.1

5.4CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

EPSS

0.4% chance of exploitation in the next 30 days; higher than 35% of CVEs (scores of 2026-10-25)

CWE

CWE-863

Published

2026-08-24

Modified

2026-10-12

Record from

the NVD, synced 2026-10-19

References

• https://codeberg.org/bookstack/bookstack/releases/tag/v26.05.4
• https://github.com/BookStackApp/BookStack/releases/tag/v26.05.4
• https://www.bookstackapp.com/blog/bookstack-release-v26-05-4/
• https://www.vulncheck.com/advisories/bookstack-broken-access-control-via-image-gallery-api

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