CVE-2026-126811

MEDIUM 5.4

BookStack before 26.09.3 Incorrect Authorization via Image and Drawio Endpoints

CVSS Score

5.4

EPSS Score

0.0%

EPSS Percentile

0th

BookStack before 26.09.3 contains an incorrect authorization vulnerability that allows authenticated users to access other users' unpublished draft page images by checking only PageView permission without draft status. Attackers can read drawio data via the base64 endpoint or rename, replace, or delete draft images by sequential ID to disclose or tamper with unpublished work.

CWE	CWE-863
Vendor	bookstackapp
Product	bookstack
Published	Nov 11, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Affected Versions

BookStackApp / BookStack

0 < 26.09.3

References

NVD ↗ CVE.org ↗ EPSS Data ↗

codeberg.org: https://codeberg.org/bookstack/bookstack/commit/926e16a23f346be47d44746d14cba40cb355cbe1 codeberg.org: https://codeberg.org/bookstack/bookstack/commit/4fec06236cbfb314fd72c1b3614c7c50162fb41c github.com: https://github.com/BookStackApp/BookStack/commit/926e16a23f346be47d44746d14cba40cb355cbe1 bookstackapp.com: https://www.bookstackapp.com/blog/bookstack-release-v26-09-3/ codeberg.org: https://codeberg.org/bookstack/bookstack/releases/tag/v26.09.3 github.com: https://github.com/BookStackApp/BookStack/releases/tag/v26.09.3 github.com: https://github.com/BookStackApp/BookStack/blob/v26.09.2/app/Uploads/Controllers/DrawioImageController.php#L82-L92 github.com: https://github.com/BookStackApp/BookStack/blob/v26.09.2/app/Uploads/Controllers/ImageController.php#L159-L169 github.com: https://github.com/fishtankyu/bookstack-draft-image-idor-advisory.md vulncheck.com: https://www.vulncheck.com/advisories/bookstack-before-26.09.3-incorrect-authorization-via-image-and-drawio-endpoints

Credits

Zeng Yu