CVE-2026-67204Network attack vector

Cross-user avatar modification via unrestricted image lookup

Published Aug 24, 2026 · Updated Aug 24, 2026

Incorrect authorization in BookStack before 26.05.4 allows remote authenticated users to alter other users' avatars through the API. The Image Gallery API controller accepts any image ID and loads avatar records without the web controller's gallery or drawing type filters. Image-update or image-delete permission plus access to a page matching uploaded_to is enough to rename, replace, or delete an avatar.

CVSS severity5.3
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Incorrect authorization in BookStack before 26.05.4 allows remote authenticated users to alter other users' avatars through the API. The Image Gallery API controller accepts any image ID and loads avatar records without the web controller's gallery or drawing type filters. Image-update or image-delete permission plus access to a page matching uploaded_to is enough to rename, replace, or delete an avatar.

The record

CVE
CVE-2026-67204
Published
Aug 24, 2026
Updated
Aug 24, 2026
Vendor
BookStack
Product
BookStack
Classifications
CWE-863, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <26.05.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

BookStack · BookStackversion=0 <26.05.4

Published CVSS scores

5.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
5.4VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo