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

Vulnerability summary

CVE-2026-42590 is a high (CVSS 8.2) Incomplete List of Disallowed Inputs vulnerability in gotenberg. EPSS estimates a 0.29% chance of exploitation in the next 30 days, higher than 21.6% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 14-05-2026
   PublishedVulnerability first disclosed.
2. 15-05-2026
   Last modifiedVulnerability information updated.

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.

• CWE-184Incomplete List of Disallowed InputsThe 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.