CVE-2025-63917: PDFPatcher XXE Vulnerability – Read Files & Launch SSRF Attacks

Published: 2025-11-17T17:15:51.207

Overview

CVE-2025-63917 identifies a critical XML External Entity (XXE) vulnerability affecting PDFPatcher versions up to and including 1.1.3.4663. This flaw resides within the application’s XML bookmark import functionality and stems from the improper handling of external entities during XML parsing. By exploiting this vulnerability, attackers can potentially read arbitrary files from the victim’s system, exfiltrate sensitive data, perform Server-Side Request Forgery (SSRF) attacks, or trigger denial-of-service conditions.

Technical Details

The root cause of CVE-2025-63917 lies in PDFPatcher’s use of the .NET XmlDocument class without disabling external entity resolution. This default configuration allows the application to process external entities defined within an XML document. An attacker can craft a malicious XML file containing an external entity declaration pointing to a local file (e.g., /etc/passwd on Linux) or an external resource. When PDFPatcher processes this crafted XML file, it will attempt to resolve the external entity, potentially revealing sensitive information or initiating connections to attacker-controlled servers.

CVSS Analysis

At the time of writing, a formal CVSS score is not available. However, based on the potential impact of the vulnerability, it would likely receive a high severity score. The ability to read arbitrary files, exfiltrate data, and perform SSRF attacks warrants serious concern.

Possible Impact

The successful exploitation of CVE-2025-63917 can lead to several severe consequences:

• Arbitrary File Read: Attackers can read sensitive files from the victim’s system, such as configuration files, password databases, or private keys.
• Data Exfiltration: Sensitive data extracted from files can be exfiltrated to an attacker-controlled server via out-of-band (OOB) HTTP requests.
• Server-Side Request Forgery (SSRF): Attackers can leverage the application to make requests to internal network resources, potentially gaining access to sensitive systems or services that are not directly exposed to the internet.
• Denial of Service (DoS): By using entity expansion techniques (e.g., Billion Laughs attack), attackers can consume excessive system resources, leading to a denial-of-service condition.

Mitigation and Patch Steps

To mitigate the risk associated with CVE-2025-63917, users of PDFPatcher are strongly advised to take the following steps:

1. Upgrade PDFPatcher: Check for and install the latest version of PDFPatcher from the official website. A patched version addressing this vulnerability should be available. If an upgrade is not yet available, consider discontinuing use of the application until a patch is released.
2. Disable XML External Entity Resolution (If possible): If you are a developer using the PDFPatcher library (if applicable, this might not be relevant for end-users), ensure that XML external entity resolution is disabled when parsing XML files. This can typically be achieved by setting the XmlResolver property of the XmlDocument object to null or a secure resolver that prohibits external entity resolution. For end-users, this might not be a directly manageable setting, underscoring the importance of upgrading to a patched version.
3. Input Validation: Implement robust input validation and sanitization techniques to prevent the injection of malicious XML code.

References