CVE-2025-56590: Apryse HTML2PDF SDK RCE Vulnerability

CVE-2025-56590 Overview

A command injection vulnerability has been discovered in the InsertFromURL() function of the Apryse HTML2PDF SDK through version 11.10. This vulnerability allows an attacker to execute arbitrary operating system commands on the local server, potentially leading to complete system compromise. The flaw exists in the way the SDK processes URL inputs, failing to properly sanitize user-controlled data before passing it to system command execution functions.

Critical Impact

Successful exploitation allows attackers to execute arbitrary operating system commands on servers running the vulnerable Apryse HTML2PDF SDK, potentially leading to data theft, system compromise, or lateral movement within the network.

Affected Products

• Apryse HTML2PDF SDK through version 11.10
• Applications utilizing the InsertFromURL() function

Discovery Timeline

• 2026-01-22 - CVE-2025-56590 published to NVD
• 2026-01-22 - Last updated in NVD database

Technical Details for CVE-2025-56590

Vulnerability Analysis

This vulnerability is classified as a Command Injection flaw that affects the InsertFromURL() function within the Apryse HTML2PDF SDK. The function is designed to fetch content from a specified URL and convert it to PDF format. However, the implementation fails to adequately validate and sanitize the URL parameter before it is processed, allowing attackers to inject malicious command arguments.

When a specially crafted URL containing operating system command syntax is passed to the vulnerable function, the underlying system executes these commands with the privileges of the application server. This argument injection attack bypasses normal application logic and directly interfaces with the operating system shell.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within the InsertFromURL() function. The function processes user-supplied URLs without proper sanitization, allowing specially crafted input to escape the intended URL context and inject additional arguments or commands that are then executed by the underlying operating system. This represents a classic case of trusting user input in a security-sensitive operation.

Attack Vector

An attacker can exploit this vulnerability by providing a maliciously crafted URL to the InsertFromURL() function. The attack requires that the attacker can influence the URL parameter passed to this function, which may occur through:

• Web applications that accept user-supplied URLs for PDF conversion
• API endpoints that process URL inputs for document generation
• Any integration point where external input reaches the vulnerable function

The vulnerability enables remote code execution when the attacker can control or manipulate the URL input to the affected function. The injected commands execute within the context of the server process, potentially granting the attacker the same privileges as the application. For detailed technical analysis of the exploitation technique, refer to the Stratascale RCE Analysis.

Detection Methods for CVE-2025-56590

Indicators of Compromise

• Unusual process spawning from the application server process running Apryse SDK
• Unexpected outbound network connections from PDF generation services
• Suspicious command-line arguments in process execution logs containing URL-like patterns with embedded commands
• Anomalous file system modifications or creation of unexpected files in application directories

Detection Strategies

• Monitor application logs for unusual URL patterns containing shell metacharacters such as backticks, semicolons, pipes, or command substitution syntax
• Implement application-layer intrusion detection rules to identify command injection attempts in URL parameters
• Review web application firewall (WAF) logs for requests targeting PDF generation endpoints with suspicious payloads
• Deploy endpoint detection and response (EDR) solutions to identify anomalous child process execution from application server processes

Monitoring Recommendations

• Enable verbose logging for all PDF generation operations and URL processing functions
• Configure SIEM rules to alert on patterns consistent with command injection attempts
• Monitor server resource utilization for unexpected CPU or memory spikes that may indicate malicious command execution
• Implement network segmentation monitoring to detect lateral movement attempts following potential exploitation

How to Mitigate CVE-2025-56590

Immediate Actions Required

• Audit all applications using Apryse HTML2PDF SDK to identify instances of the InsertFromURL() function
• Implement strict input validation on all URLs passed to the vulnerable function, including allowlisting of permitted URL schemes and domains
• Consider temporarily disabling the InsertFromURL() functionality until a patch is available
• Deploy web application firewall rules to block requests containing command injection patterns

Patch Information

Monitor the Apryse official website for security updates and patched versions of the HTML2PDF SDK. Organizations should subscribe to Apryse security notifications and apply updates as soon as they become available. Until an official patch is released, implement the workarounds described below.

Workarounds

• Implement strict URL validation using allowlists that only permit trusted domains and URL schemes (http/https only)
• Sanitize all user input by removing or encoding shell metacharacters before passing to the InsertFromURL() function
• Run the application with minimal privileges to limit the impact of potential command execution
• Deploy network-level controls to restrict outbound connections from servers running the vulnerable SDK
• Consider using alternative PDF generation methods that do not rely on the vulnerable InsertFromURL() function

# Example URL validation configuration (application-level)
# Implement strict URL allowlisting before passing to InsertFromURL()
ALLOWED_DOMAINS="trusted-domain.com,internal-server.local"
ALLOWED_SCHEMES="https"

# Ensure URLs are validated against these restrictions
# Reject any URL containing shell metacharacters: ; | & ` $ ( ) { }