Full Report
A critical heap buffer overflow vulnerability (CVE-2026-39919) in the Ghostscript interpreter and rendering engine could allow remote code execution through specially crafted PDF files. [...]
Analysis Summary
# Vulnerability: Critical Heap Buffer Overflow in Ghostscript (CVE-2026-39919)
## CVE Details
- **CVE ID:** CVE-2026-39919
- **CVSS Score:** Not explicitly rated in the text, but categorized as **Critical**.
- **CWE:** CWE-122 (Heap-based Buffer Overflow)
## Affected Systems
- **Products:** Ghostscript interpreter and rendering engine.
- **Versions:** Affected versions range from **9.21 through 10.07.1**.
- **Configurations:**
- Systems using **ImageMagick** via the PHP **Imagick** extension (common in WordPress).
- Online systems that process/render user-uploaded PDF files to generate thumbnails or previews.
- Affected OS environments include Debian, Ubuntu, Fedora, Alpine, and AlmaLinux.
## Vulnerability Description
The flaw is a heap buffer overflow triggered when Ghostscript processes a specially crafted PDF file containing a **JPEG 2000** image. The engine incorrectly handles low-bit-depth samples and mismatched component resolutions. Specifically, the vulnerability allows an attacker to force Ghostscript to write 1,024 bytes into a 256-byte buffer, leading to memory corruption and potential unauthenticated Remote Code Execution (RCE).
## Exploitation
- **Status:** PoC available (developed by Wordfence researchers); Not currently observed exploited in the wild.
- **Complexity:** Medium to High (Success depends on environmental factors such as fonts, language settings, and system libraries).
- **Attack Vector:** Network (Remote via PDF upload).
## Impact
- **Confidentiality:** High (Potential for full server takeover).
- **Integrity:** High (Ability to execute arbitrary code).
- **Availability:** High (System crash or unauthorized persistent access).
## Remediation
### Patches
- **Ghostscript Version 10.08.0:** This version contains the official fix rolled out on September 8.
- **Backported Fixes:** Users on older versions should check their specific distribution's revision history for backported security patches.
### Workarounds
- **Block PDF Uploads:** Disable the ability for users (especially anonymous or low-privileged) to upload PDF files.
- **Disable PDF Rendering:** Configure ImageMagick policies to disable the rendering of PDF files.
- **Container Updates:** Rebuild and redeploy Docker containers using updated base images that include Ghostscript 10.08.0+.
## Detection
- **Indicators of Compromise:** Unusual outbound network traffic from web servers, unauthorized shell execution, or unexpected file modifications in the web root.
- **Detection Methods:**
- Verify Ghostscript version via command line (`gs --version`).
- Use vulnerability scanners to identify outdated instances of Ghostscript and ImageMagick.
- Monitor for failed PDF rendering processes that might indicate exploitation attempts (crashes).
## References
- Artifex (Ghostscript Maintainer): [https://www.ghostscript.com/](https://www.ghostscript.com/)
- Wordfence (Original Research): [https://www.wordfence.com/](https://www.wordfence.com/)
- Bleeping Computer Article: [https://www.bleepingcomputer.com/news/security/ghostscript-flaw-lets-hackers-hijack-servers-via-pdf-uploads/](https://www.bleepingcomputer.com/news/security/ghostscript-flaw-lets-hackers-hijack-servers-via-pdf-uploads/)