The CVE-2025-46646 identifies a notable vulnerability that exists in Artifex Ghostscript software versions before 10.05.. Ghostscript is a popular and versatile open-source software suite providing applications for working with documents in the PostScript and PDF file formats. The vulnerability stems from an incomplete fix for a previous issue, CVE-2024-46954, and affects the decode_utf8 function in base/gp_utf8.c.

In this long-read post, we will dive into the specifics of this vulnerability, look at code snippets, discuss the exploit details, and provide links to original references. It is important to note that the vulnerability may have severe consequences on the impacted systems, and hence warrants thorough understanding and timely remediation.

Vulnerability Details

This vulnerability is classified as an overlong UTF-8 encoding issue in the Ghostscript software. The affected decode_utf8 function in the base/gp_utf8.c file mishandles overlong UTF-8 encoded strings. Overlong UTF-8 encoding occurs when a character is represented using more bytes than needed, potentially allowing malicious exploitation of the flaw.

Here is a code snippet from the decode_utf8 function, illustrating the incomplete fix for CVE-2024-46954:

int
gp_decode_utf8(const byte * p, uint * pvalue)
{
    int size = 1;
    uint value;

    if (p[] < x80) {
        value = p[];
    } else if ((p[] & xE) == xC) {
        size = 2;
        value = p[] & x1F;
        if (value < 2)		/* incomplete fix for CVE-2024-46954 */
            return -1;
    } else {
        /* ... Rest of the function ... */
    }
    /* ... */
}

As seen in the code snippet above, the incomplete fix does not handle all possible overlong encoding scenarios.

Exploit Details

An attacker can exploit the vulnerability in CVE-2025-46646 using carefully-crafted overlong UTF-8 encoded strings, which might bypass security checks and lead to arbitrary code execution, denial of service, or privilege escalation. This could allow a remote attacker to compromise the integrity, confidentiality, and availability of the affected systems.

Since Ghostscript has widespread use in applications such as image viewers and file converters, the exploitation of this vulnerability poses significant risks to end users and organizations alike.

Original References

The GitHub repository for Ghostscript and the associated commit for this vulnerability are available at the following links:

1. GitHub Repository: Ghostscript
2. Commit Fixing CVE-2025-46646: ArtifexSoftware/ghostpdl@4c04590

These resources provide valuable insights into the vulnerability's history and potential impact.

Conclusion

CVE-2025-46646, the overlong UTF-8 encoding issue in Artifex Ghostscript before version 10.05., is a critical vulnerability that must be addressed to prevent potential system compromises. System administrators and developers using Ghostscript should take swift action to update to version 10.05. or later and ensure that security checks are in place to handle maliciously-crafted strings.

This informative post has laid out the vulnerability details, exploit information, and original references to aid in the understanding and remediation of the CVE-2025-46646 vulnerability. Stay vigilant, stay secure, and stay updated!

Timeline

Published on: 04/26/2025 15:15:45 UTC
Last modified on: 04/29/2025 13:52:10 UTC