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Remote Code Execution Through Image Uploads in BookStack

High severity GitHub Reviewed Published Mar 8, 2020 in BookStackApp/BookStack • Updated Jan 9, 2023

Package

composer ssddanbrown/bookstack (Composer)

Affected versions

< 0.25.3

Patched versions

0.25.5

Description

Impact

A user could upload PHP files through image upload functions, which would allow them to execute code on the host system remotely. They would then have the permissions of the PHP process.

This most impacts scenarios where non-trusted users are given permission to upload images in any area of the application.

Patches

The issue was addressed in a series of patches: v0.25.3, v0.25.4 and v0.25.5.
Users should upgrade to at least v0.25.5 to avoid this patch but ideally the latest BookStack version as previous versions are un-supported.

Workarounds

Depending on BookStack version, you could use the local_secure image storage option, or use s3 or a similar compatible service.

Preventing direct execution of any php files, apart from the public/index.php file, though web-server configuration would also prevent this.

References

BookStack Beta v0.25.3
BookStack Beta v0.25.4
BookStack Beta v0.25.5

For more information

If you have any questions or comments about this advisory:

References

@ssddanbrown ssddanbrown published to BookStackApp/BookStack Mar 8, 2020
Reviewed Mar 13, 2020
Published to the GitHub Advisory Database Mar 13, 2020
Last updated Jan 9, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:L

EPSS score

0.244%
(64th percentile)

Weaknesses

CVE ID

CVE-2020-5256

GHSA ID

GHSA-g9rq-x4fj-f5hx

Source code

No known source code

Credits

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