In today's digital landscape, the security of software applications is of the utmost importance. Vulnerabilities such as the one we will discuss in this post can lead to devastating consequences if left unaddressed. In this long read, we dive deep into CVE-2025-27835, a dangerous buffer overflow vulnerability discovered in Artifex Ghostscript versions prior to 10.05.. We’ll examine the exploit details, relevant code snippets, and share links to original references.

What is Artifex Ghostscript?

Artifex Ghostscript is a high-quality developer tool suite for interpreting and rendering PDF and PostScript files. It is widely used by graphic designers, developers, and printing professionals. You can learn more about Ghostscript and its extensive features here: Artifex Ghostscript

The Vulnerability: CVE-2025-27835

CVE-2025-27835, assigned by the Common Vulnerabilities and Exposures (CVE) system, is a critical security issue discovered in Artifex Ghostscript before version 10.05.. This buffer overflow vulnerability can compromise the target application's memory, leading to potential attacks including denial of service, unauthorized access, and data corruption.

The issue arises due to improper handling of glyph conversion to Unicode characters in the psi/zbfont.c file. A malicious actor can exploit this vulnerability by crafting a specially designed PDF or PostScript file. Opening this file using a vulnerable Ghostscript version can trigger the buffer overflow, leading to the aforementioned security risks.

Code Snippet: The Vulnerable Part in Ghostscript

The buffer overflow occurs in the psi/zbfont.c file of Ghostscript. The problematic code snippet is as follows:

int zfont2_glyph_info(gs_font *font, gs_glyph glyph, const gs_matrix *pmat, ushort upem, unsigned int mask, void *data, int *width, bool incl)
{
    ...
    uchar buf[6];
    ...
    punicode = (uchar *) ialloc_bytes(i_ctx_p, upem * 2, "zfont2_glyph_name");
    ...
    for (i = , l = ; i < upem; i++) {
        ushort u = punicode[i];
        uchar buf[6];
        int l1 = snprintf(buf, sizeof(buf), "uni%04hx", u);
        ...
    }
    ...
}

In this snippet, the uchar buf[6] declaration allocates a fixed-size buffer of six bytes. However, the buffer size handling is flawed during the conversion of glyphs to Unicode characters, which can cause the overflow.

How to Exploit CVE-2025-27835

There are currently no reports of CVE-2025-27835 being exploited in the wild. However, security researchers and developers must remain vigilant, as this vulnerability can be weaponized for cyberattacks.

To exploit this buffer overflow, an attacker would create a malicious PDF or PostScript file containing crafted glyphs that trigger the overflow when processed using a vulnerable version of Artifex Ghostscript. The attacker would then deliver this malicious file to the victim - via phishing, drive-by downloads, or other social engineering techniques - and convince them to open it with Ghostscript.

Mitigating the Threat

To protect yourself against this vulnerability, it is imperative to update your Ghostscript version to 10.05. or later. Artifex has addressed the buffer overflow in this release, effectively mitigating the threat posed by CVE-2025-27835. You can download the latest version of Ghostscript here: Ghostscript Download

Additional Resources

- Ghostscript Announcement for Ghostscript 10.05.
- NVD - CVE-2025-27835

Conclusion

In conclusion, CVE-2025-27835 is a dangerous buffer overflow vulnerability affecting Artifex Ghostscript versions prior to 10.05.. By understanding and mitigating this vulnerability, users and developers can maintain the security and integrity of their digital assets. Keeping Ghostscript up-to-date and staying informed about potential cyber threats are essential to staying protected in today's digital landscape.

Timeline

Published on: 03/25/2025 21:15:43 UTC
Last modified on: 03/27/2025 16:45:46 UTC