OP 14 October, 2026 - 08:48 PM
(This post was last modified: 14 October, 2026 - 08:48 PM by chandlrr.)
A critical heap buffer overflow vulnerability (CVE-2026-39919) in the Ghostscript interpreter and rendering engine could allow remote code execution using specially crafted PDFs. The vulnerability was discovered on August 23 by researchers at the Defiant Wordfence platform using their AI-powered system Argus.bleepingcomputer
What is Ghostscript
Ghostscript is a PostScript and PDF interpreter that can display PDFs as images, create thumbnails for previews, and optimize PDFs by compressing embedded images and removing unnecessary font data.bleepingcomputer
When creating a PDF thumbnail, WordPress can use the Imagick PHP extension to call ImageMagick, which runs Ghostscript.bleepingcomputer
When creating a PDF thumbnail, WordPress can use the Imagick PHP extension to call ImageMagick, which runs Ghostscript.bleepingcomputer
How the vulnerability works
A specially crafted PDF containing a JPEG 2000 image can cause incorrect processing of low-bit samples and mismatched component resolutions.bleepingcomputer
Using Argus, researchers developed two exploits for CVE-2026-39919 that cause Ghostscript to write 1,024 bytes to a 256-byte buffer, corrupting adjacent memory and leading to unauthenticated remote code execution in the WordPress deployment. bleepingcomputer
Wordfence has focused on WordPress systems, but notes that the vulnerability affects any online system running on Ghostscript 9.21–10.07.1 and can be exploited if the payload is adapted to the bleepingcomputer environment
Using Argus, researchers developed two exploits for CVE-2026-39919 that cause Ghostscript to write 1,024 bytes to a 256-byte buffer, corrupting adjacent memory and leading to unauthenticated remote code execution in the WordPress deployment. bleepingcomputer
Wordfence has focused on WordPress systems, but notes that the vulnerability affects any online system running on Ghostscript 9.21–10.07.1 and can be exploited if the payload is adapted to the bleepingcomputer environment
Tested environments
The researchers tested ten Linux environments, including Debian, Ubuntu, Fedora, Alpine, and AlmaLinux, as well as an official snapshot of the WordPress Docker image, and found that all of them contained vulnerable code.bleepingcomputer
Tested environments
Source: Wordfencebleepingcomputer
The researchers tested two proof-of-concept (PoC) exploits and found that their ability to cause the vulnerability depended on the target environment.bleepingcomputer
In the lab bench, they executed exploits 10,240 times against Linux packages, but were unable to achieve remote code execution. However, they successfully executed the code remotely on a specially created test server.bleepingcomputer
The researchers found that changing PDF fonts, language settings, font configuration, and one core system library allowed the exploit to work, albeit not reliably.bleepingcomputer
Tested environments
Source: Wordfencebleepingcomputer
The researchers tested two proof-of-concept (PoC) exploits and found that their ability to cause the vulnerability depended on the target environment.bleepingcomputer
In the lab bench, they executed exploits 10,240 times against Linux packages, but were unable to achieve remote code execution. However, they successfully executed the code remotely on a specially created test server.bleepingcomputer
The researchers found that changing PDF fonts, language settings, font configuration, and one core system library allowed the exploit to work, albeit not reliably.bleepingcomputer
Terms of Use in WordPress
In particular, four conditions are necessary for successful operation in WordPress environments:bleepingcomputer
- An attacker can download a PDF anonymously or through a low-privileged account.
- The site processes this PDF to create a preview or thumbnail.
- The processing chain reaches Ghostscript, with the necessary software settings and policies allowing PDF rendering.
- Ghostscript contains unpatched vulnerable decoding code.
Wordfence noted that standard WordPress does not allow anonymous uploads to the Media Library.bleepingcomputer
More generally, any application that displays attacker-provided PDFs via affected Ghostscript code may be affected by this vulnerability, and the authentication requirements for exploitation depend on the .bleepingcomputer application
More generally, any application that displays attacker-provided PDFs via affected Ghostscript code may be affected by this vulnerability, and the authentication requirements for exploitation depend on the .bleepingcomputer application
Correction and recommendations
Artifex, the developer of Ghostscript, released a fix on September 8 in version 10.08.0 of the interpreter. Fixes have also been ported back to older versions, so users should check the revision details for patch status.bleepingcomputer
WordPress administrators need to check with their hosting provider that Ghostscript is updated to version 10.08.0 or later.bleepingcomputer
WordPress administrators need to check with their hosting provider that Ghostscript is updated to version 10.08.0 or later.bleepingcomputer
- If using Docker, it is recommended to rebuild and redeploy the system using an updated, patched base image.
- If upgrading to a fixed version of Ghostscript is not possible, it is recommended that you block PDF files from being uploaded to the server or disable PDF rendering in ImageMagick.bleepingcomputer
Wordfence said it has not yet observed CVE-2026-39919 being exploited in the wild.
source : https://www.bleepingcomputer.com/news/se...f-uploads/
source : https://www.bleepingcomputer.com/news/se...f-uploads/
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