CVE-2025-6660: PDF-XChange Editor GIF Parsing RCE Flaw

CVE-2025-6660 Overview

CVE-2025-6660 is a heap-based buffer overflow vulnerability [CWE-122] in PDF-XChange Editor's GIF file parsing logic. The flaw allows attackers to execute arbitrary code in the context of the current user process. Exploitation requires user interaction: the target must open a crafted file or visit a malicious page that delivers one. The vulnerability was reported through the Zero Day Initiative as ZDI-CAN-26763 and tracked publicly as ZDI-25-443. PDF-XChange Editor, PDF-XChange Pro, and PDF-Tools version 10.5.2.395 are affected.

Critical Impact
Attackers can achieve arbitrary code execution on affected installations by tricking a user into opening a malicious GIF embedded in or referenced by a PDF document.

Affected Products

PDF-XChange Editor 10.5.2.395
PDF-XChange Pro 10.5.2.395
PDF-XChange PDF-Tools 10.5.2.395

Discovery Timeline

2025-06-25 - CVE-2025-6660 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-6660

Vulnerability Analysis

The vulnerability resides in the GIF file parsing routines used by PDF-XChange Editor. The parser fails to validate the length of user-supplied data before copying it into a fixed-length heap-allocated buffer. When an attacker-controlled GIF stream provides more data than the destination buffer can hold, adjacent heap metadata and objects are overwritten. Attackers can shape the heap layout and overwrite function pointers or vtables to redirect execution. Because PDF documents can embed or reference image streams, the malicious GIF can be delivered inside a seemingly benign PDF.

Root Cause

The root cause is improper bounds checking during GIF decoding. The parser assumes that length fields within the GIF stream correspond to the size of the receiving heap buffer. By supplying inconsistent or oversized length metadata, an attacker forces the copy operation to exceed the buffer boundary, classified under CWE-122 (Heap-based Buffer Overflow).

Attack Vector

Exploitation requires the victim to open a malicious file or browse to a page that supplies one. The attack runs at the privilege level of the user executing PDF-XChange Editor. A successful exploit yields arbitrary code execution within the application process, which can then be chained with privilege escalation primitives or used as an initial access vector to drop additional payloads.

No public proof-of-concept code has been released. Technical details are referenced in the Zero Day Initiative Advisory ZDI-25-443.

Detection Methods for CVE-2025-6660

Indicators of Compromise

Unexpected child processes spawned by PDFXEdit.exe or related PDF-XChange binaries, such as cmd.exe, powershell.exe, or rundll32.exe.
PDF documents containing embedded or referenced GIF streams with malformed Logical Screen Descriptor or Image Descriptor length fields.
Crash dumps or Windows Error Reporting events involving heap corruption in PDF-XChange Editor processes.

Detection Strategies

Hunt for process lineage where PDF-XChange binaries spawn scripting interpreters or command shells.
Inspect inbound email attachments and downloaded PDFs for embedded GIF objects with anomalous header sizes.
Monitor endpoints running PDF-XChange Editor, PDF-XChange Pro, or PDF-Tools 10.5.2.395 for behavioral anomalies during file opens.

Monitoring Recommendations

Enable command-line argument logging and process creation auditing on systems where PDF-XChange products are installed.
Collect and centralize Windows Error Reporting telemetry to surface exploitation attempts that fail mid-execution.
Track outbound network connections initiated by PDF-XChange processes immediately after document open events.

How to Mitigate CVE-2025-6660

Immediate Actions Required

Inventory all systems running PDF-XChange Editor, PDF-XChange Pro, or PDF-Tools and identify any instances at version 10.5.2.395 or earlier.
Apply the vendor-provided update referenced in the PDF-XChange Security Bulletins as soon as it is available in your environment.
Restrict opening PDF documents from untrusted sources until patching is complete.

Patch Information

PDF-XChange has published remediation details on its security bulletins page. Administrators should upgrade affected installations to a fixed version newer than 10.5.2.395. Additional technical context is available in the Zero Day Initiative Advisory ZDI-25-443.

Workarounds

Set a different default PDF reader on endpoints that cannot be immediately patched, removing PDF-XChange Editor from the file-association attack surface.
Block or quarantine PDF attachments at the mail gateway when they originate from untrusted senders.
Educate users not to open unsolicited PDF documents and to verify file origins before opening.

bash

# Configuration example: enumerate affected PDF-XChange installations on Windows endpoints
Get-WmiObject -Class Win32_Product | Where-Object {
    $_.Name -like 'PDF-XChange*' -and $_.Version -le '10.5.2.395'
} | Select-Object Name, Version, InstallDate