Gotenberg up to 8.29.x PDF File Writer.pl File:FileName incomplete blacklist

Summaryinfo

A vulnerability was found in Gotenberg up to 8.29.x and classified as critical. The impacted element is an unknown function of the file Writer.pl of the component PDF File Handler. Such manipulation of the argument File:FileName leads to incomplete blacklist. This vulnerability is referenced as CVE-2026-42590. It is possible to launch the attack remotely. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Gotenberg up to 8.29.x and classified as critical. Affected by this issue is an unknown code of the file Writer.pl of the component PDF File Handler. The manipulation of the argument File:FileName with an unknown input leads to a incomplete blacklist vulnerability. Using CWE to declare the problem leads to CWE-184. The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete, leading to resultant weaknesses. Impacted is integrity, and availability. CVE summarizes:

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.30.0, The ExifTool metadata write blocklist in Gotenberg can be bypassed using ExifTool's group-prefix syntax, enabling arbitrary file rename, move, hardlink, and symlink creation on the server. ExifTool supports group-prefix syntax where File:FileName is processed identically to FileName -- the prefix is stripped by SetNewValue in Writer.pl before tag matching. The safeKeyPattern regex (^[a-zA-Z0-9\-_.:]+$) allows colons, so prefixed tag names pass validation. Any prefix works: File:FileName, System:Directory, a:HardLink, etc. Additionally, FilePermissions, FileUserID, and FileGroupID pseudo-tags are not blocked at all and can modify file attributes without any prefix. This vulnerability is fixed in 8.30.0.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-42590 since 04/29/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1562.006.

Upgrading to version 8.30.0 eliminates this vulnerability.

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Productinfo

Name

• Gotenberg

Version

• 8.0
• 8.1
• 8.2
• 8.3
• 8.4
• 8.5
• 8.6
• 8.7
• 8.8
• 8.9
• 8.10
• 8.11
• 8.12
• 8.13
• 8.14
• 8.15
• 8.16
• 8.17
• 8.18
• 8.19
• 8.20
• 8.21
• 8.22
• 8.23
• 8.24
• 8.25
• 8.26
• 8.27
• 8.28
• 8.29

Website

• Product: https://github.com/gotenberg/gotenberg/

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