CVE-2021-3781: Ghostscript -dSAFER sandbox escape via crafted pipe command

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 18 September 2026. Confidence: medium.

critical priorityCVSS 9.9 critical with scope change and very high EPSS, though no KEV listing or confirmed in-the-wild exploitation is recorded.

What it is

Ghostscript's -dSAFER sandbox can be escaped by injecting a specially crafted pipe command, allowing a malicious document to run arbitrary commands as the interpreter. Because Ghostscript is widely embedded in document conversion and printing pipelines, untrusted files can turn into host command execution. The record gives no affected version ranges, so version-specific exposure cannot be confirmed from it.

Impact

An attacker gains arbitrary command execution in the context of the Ghostscript interpreter, threatening confidentiality, integrity and availability of the host. The CVSS scope change (S:C) indicates impact can extend beyond the vulnerable component.

Attack surface

Reached over the network (AV:N) by supplying a crafted document to a Ghostscript-based processing path; no user interaction is required (UI:N). The vector requires low privileges (PR:L), so the attacker needs some existing access or a service context that processes their input.

Exploitation

Not listed in CISA KEV and no ransomware use documented, but EPSS is very high (0.839, 99.7th percentile), indicating strong likelihood of exploitation activity. References are patch and advisory links only, with no public exploit tag.

What to do

• Patch Ghostscript to a fixed release using the vendor advisory and Red Hat bug 2002271 as guidance.
• If patching is delayed, avoid processing untrusted documents with Ghostscript and disable or restrict -dSAFER-dependent conversion services.
• Run Ghostscript in a hardened sandbox or container with minimal filesystem and network access, since -dSAFER itself is the escape vector.
• Restrict who can submit documents to Ghostscript-backed pipelines, given the PR:L requirement.
• Track vendor advisories (Artifex, Fedora, Gentoo GLSA 202211-11) for updated fixed versions.

Detection

• Monitor Ghostscript processes for unexpected child processes or shell execution, especially pipe-related commands.
• Alert on Ghostscript handling files from untrusted or external sources outside normal workflow.
• Review host logs for command execution spawned by document conversion or print services.
• Watch for anomalous outbound network connections from hosts running Ghostscript-based services.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.