CVE-2026-42589: Gotenberg has Unauthenticated RCE via ExifTool Metadata Key Injection

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 3.7%, percentile 90: FIRST’s model estimates a 3.7% chance of exploitation activity in the next 30 days, higher than 90% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes github.com/gotenberg/gotenberg/v8 (Go) = 8.29.1, no fixed version listed. Check your lockfile, including transitive dependencies.

What it is

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, Gotenberg's /forms/pdfengines/metadata/write HTTP endpoint accepts a JSON metadata object and passes its keys directly to ExifTool via the go-exiftool library. No validation is performed on key characters. A \n embedded in a JSON key splits the ExifTool stdin stream into a new argument line, allowing an attacker to inject arbitrary ExifTool flags — including -if, which evaluates Perl expressions. This achieves unauthenticated OS command execution in a single HTTP request. The response is HTTP 200 with a valid PDF, making the attack transparent to basic monitoring. This vulnerability is fixed in 8.31.0.

From the GitHub advisory

Unauthenticated RCE in Gotenberg via Metadata Key Newline Injection

Summary

Gotenberg's /forms/pdfengines/metadata/write HTTP endpoint accepts a JSON metadata object and passes its keys directly to ExifTool via the go-exiftool library. No validation is performed on key characters. A \n embedded in a JSON key splits the ExifTool stdin stream into a new argument line, allowing an attacker to inject arbitrary ExifTool flags — including -if, which evaluates Perl expressions. This achieves unauthenticated OS command execution in a single HTTP request. The response is HTTP 200 with a valid PDF, making the attack transparent to basic monitoring.

Vulnerability Details

| Field | Value | |------------------|------------------------------------------| | Product | Gotenberg | | Version | 8.29.1 (default gotenberg/gotenberg:8) | | Component | pdfengines/metadata/write endpoint | | CWE | CWE-78 — Improper Neutralization of Special Elements used in an OS Command |

Weakness type: CWE-78.

Product: github.com/gotenberg/gotenberg/v8 (Go) · Assigned by: GitHub_M · Published: 2026-05-14

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 3.67% probability of exploitation activity in the next 30 days; percentile 90.

Timeline

• 2026-05-07 — GitHub-reviewed advisory GHSA-rqgh-gxv4-6657 published (critical)
• 2026-05-14 — CVE record last updated
• 2026-05-14 — CVE record published by GitHub_M

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-rqgh-gxv4-6657 github.com
2. CVE.org record CVE-2026-42589 cve.org
3. NVD entry CVE-2026-42589 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com

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