CVE-2025-7462

Executive Summary

CVE-2025-7462 is a null pointer dereference vulnerability found in Artifex GhostPDL, specifically within the pdf_ferror function in devices/vector/gdevpdf.c. The vulnerability is triggered when handling errors during the opening of a new output file, leading to a null pointer dereference. This issue can be exploited remotely, potentially causing a denial of service (DoS) by crashing the application. The vulnerability affects versions up to commit 3989415a5b8e99b9d1b87cc9902bde9b7cdea145. A patch is available in commit 619a106ba4c4abed95110f84d5efcd7aee38c7cb. No public proof-of-concept (PoC) or exploit code has been identified at this time.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects the Artifex GhostPDL software, which is a suite of interpreters for PostScript and PDF languages. Users should verify the integrity of their GhostPDL installations and apply the patch from the official repository.

CVSS Breakdown & Threat Level

The CVSS score is currently 0.0, indicating that no official CVSS vector has been assigned. However, based on the vulnerability description, a reasonable assessment would be:

• Attack Vector (AV): Network (N) – The attack can be initiated remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – The user must open a malicious file or trigger the error condition.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – The null pointer dereference leads to a crash, causing denial of service.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Threat Level: Medium. The vulnerability is remotely exploitable but requires user interaction and only results in a denial of service.

Deep Dive & Mechanics

The vulnerability resides in the pdf_ferror function within the file devices/vector/gdevpdf.c. This function is part of the error handling mechanism when a new output file fails to open. The issue occurs because the function attempts to access a pointer that has not been properly initialized or has been set to NULL after a failed file open operation.

When GhostPDL processes a PDF or PostScript file and encounters an error while opening a new output file (e.g., due to a malformed file or resource exhaustion), the error handler pdf_ferror is invoked. Inside this handler, the code dereferences a pointer without checking if it is NULL. This leads to a null pointer dereference, causing the application to crash.

The vulnerable code path is triggered when:

1. A user opens a specially crafted PDF or PostScript file.
2. The file causes an error during the output file creation process.
3. The error handler pdf_ferror is called, which then dereferences a NULL pointer.

The patch (commit 619a106ba4c4abed95110f84d5efcd7aee38c7cb) adds a NULL check before dereferencing the pointer, preventing the crash.

Vulnerable vs. Patched Code

Vulnerable Code (simplified):

void pdf_ferror(gx_device *dev) {
    pdf_device *pdev = (pdf_device *)dev;
    // ... other code ...
    // Directly dereference without NULL check
    pdev->some_field = value;
    // ...
}

Patched Code (simplified):

void pdf_ferror(gx_device *dev) {
    pdf_device *pdev = (pdf_device *)dev;
    if (pdev == NULL) {
        // Handle error gracefully
        return;
    }
    // ... other code ...
    pdev->some_field = value;
    // ...
}

The patch ensures that the pointer pdev is checked for NULL before any dereference occurs. This prevents the null pointer dereference and subsequent crash.

Exploitation & Lab Setup

Red Team

Objective: Trigger a denial of service (DoS) by causing a null pointer dereference in GhostPDL.

Lab Setup:

1. Install a vulnerable version of GhostPDL (commit before 619a106ba4c4abed95110f84d5efcd7aee38c7cb).
2. Create a malicious PDF file that triggers an error during output file creation. This can be achieved by crafting a PDF that references a non-existent output file or causes a resource exhaustion condition.

Exploitation Steps:

1. Prepare a malicious PDF file that forces GhostPDL to attempt to open a new output file in a way that fails.
2. Send the file to the target system or trick a user into opening it with GhostPDL.
3. When GhostPDL processes the file, the error handler pdf_ferror is called, leading to a null pointer dereference and crash.

Note: No public exploit code is available. The above steps are based on the vulnerability description.

Blue Team

Detection:

• Monitor for crashes of GhostPDL processes.
• Look for error logs indicating a null pointer dereference in gdevpdf.c.
• Use file integrity monitoring to detect unauthorized modifications to GhostPDL binaries.

Mitigation:

• Apply the patch from commit 619a106ba4c4abed95110f84d5efcd7aee38c7cb.
• Restrict the use of GhostPDL to trusted files only.
• Implement application whitelisting to prevent execution of untrusted PDFs.

Indicators of Compromise (IOCs)

• File Hashes: No specific file hashes are available for malicious files.
• Process Anomalies: GhostPDL process crashes with a segmentation fault or null pointer dereference error.
• Log Entries: Error messages containing "pdf_ferror" or "null pointer" in GhostPDL logs.
• Network Traffic: No specific network indicators; the attack is file-based.

Detection Engineering

YARA Rule

rule CVE_2025_7462_GhostPDL_Null_Pointer {
    meta:
        description = "Detects potential exploitation of CVE-2025-7462 in GhostPDL"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-7462"
    strings:
        $s1 = "pdf_ferror" ascii wide nocase
        $s2 = "gdevpdf.c" ascii wide nocase
        $s3 = "null pointer" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: GhostPDL Null Pointer Dereference (CVE-2025-7462)
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects crashes or error messages related to CVE-2025-7462 in GhostPDL
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "pdf_ferror"
        - "gdevpdf.c"
        - "null pointer"
    condition: selection
falsepositives:
    - Legitimate crashes due to other bugs
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-7462 GhostPDL Null Pointer Dereference Attempt"; flow:to_server,established; content:"pdf_ferror"; nocase; content:"gdevpdf.c"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

1. Apply the Patch: Update GhostPDL to a version that includes commit 619a106ba4c4abed95110f84d5efcd7aee38c7cb or later.
2. Input Validation: Ensure that files processed by GhostPDL are from trusted sources.
3. Sandboxing: Run GhostPDL in a sandboxed environment to limit the impact of a crash.
4. Monitoring: Implement detection rules (YARA, Sigma, Suricata) to identify exploitation attempts.
5. User Education: Train users to avoid opening untrusted PDF or PostScript files.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert