CVE-2026-42590: Gotenberg: ExifTool group-prefix syntax bypasses dangerous-tag blocklist

Severity: high (CVSS 8.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-14 · updated 2026-06-17
Weakness: CWE-184

Description

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.

Affected products

gotenberg: before 8.30.0 — fixed in 8.30.0

How to fix

Upgrade to a fixed version: gotenberg 8.30.0. Check the vendor advisory for mitigations.

References

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