CVE-2026-67204: Auth Bypass (CVSS 5.4)

Description

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.

Is your site exposed to CVE-2026-67204?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

5.4

MEDIUM

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

EPSS — Exploit Prediction

0.0024

Probability of exploitation

0.15%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-863 Incorrect Authorization

References

Other 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

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 5.4 (MEDIUM).

How severe is CVE-2026-67204? +

CVE-2026-67204 has a CVSS v3.1 score of 5.4 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0024, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-67204? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-84355

Incorrect authorization in Navigation in Google Chrome prior to 152.0.7977.75 allowed a remote attacker who had compromised the renderer process …

CVE-2026-65601

Traefik versions 3.7.0 through 3.7.6 contain a namespace confusion vulnerability in the Kubernetes Gateway API provider. When resolving HTTPRoute.spec.rules[].backendRefs[].filters[].extensionRef, Traefik …

CVE-2026-50008

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. From version …

CVE-2026-15829

A SQL injection (CWE-89) and security boundary bypass (CWE-863) vulnerability exists in the prebuilt BigQuery forecasting tool (bigquery-forecast) of googleapis/mcp-toolbox. …

CVE-2026-42571

Pelican is a platform for creating data federations. From versions 7.21.0 to before 7.21.5, 7.22.0 to before 7.22.3, 7.23.0 to …

CVE-2026-42137

Kirby is an open-source content management system. Prior to versions 4.9.0 and 5.4.0, `pages.access/list` and `files.access/list` permissions are not consistently …

CVE-2026-67204