CVE-2025-25977: Canvg RCE Vulnerability

CVE-2025-25977 Overview

CVE-2025-25977 is a critical arbitrary code execution vulnerability affecting the canvg library version 4.0.2. The vulnerability exists in the Constructor of the StyleElement class, which can be exploited by attackers to execute arbitrary code. Canvg is a popular JavaScript library used for parsing and rendering SVG documents in web browsers and Node.js environments, making this vulnerability particularly concerning for applications that process user-supplied SVG content.

Critical Impact

Attackers can achieve remote code execution through the vulnerable StyleElement class constructor, potentially leading to complete system compromise in applications using the affected canvg version.

Affected Products

• canvg version 4.0.2
• Applications and services using canvg v.4.0.2 for SVG processing
• Node.js and browser-based environments utilizing the vulnerable library

Discovery Timeline

• 2025-03-10 - CVE-2025-25977 published to NVD
• 2025-03-25 - Last updated in NVD database

Technical Details for CVE-2025-25977

Vulnerability Analysis

This vulnerability is classified under CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes, commonly known as 'Prototype Pollution'). The flaw resides within the StyleElement class constructor in canvg v.4.0.2. When processing maliciously crafted input, the constructor fails to properly validate or sanitize data, allowing an attacker to inject and execute arbitrary code.

The network-accessible nature of this vulnerability means attackers can exploit it remotely without authentication or user interaction. Applications that accept SVG content from untrusted sources and process it using the vulnerable canvg library are at significant risk.

Root Cause

The root cause stems from insufficient input validation within the StyleElement class constructor. When the constructor processes style-related data from SVG documents, it does not adequately sanitize or restrict the input, creating an opportunity for prototype pollution or code injection attacks. This allows malicious payloads embedded in SVG content to be executed in the context of the application.

Attack Vector

The attack is network-based and can be executed without any privileges or user interaction. An attacker would craft a malicious SVG document containing specially constructed style elements. When a vulnerable application processes this SVG using canvg v.4.0.2, the payload within the StyleElement constructor is executed, granting the attacker arbitrary code execution capabilities.

The vulnerability is particularly dangerous in scenarios where:

• Web applications allow users to upload or embed SVG content
• Server-side applications render SVG documents using canvg
• PDF generators or image processing services utilize canvg for SVG conversion

For technical details and discussion, see the GitHub Issue Tracker Entry.

Detection Methods for CVE-2025-25977

Indicators of Compromise

• Presence of canvg version 4.0.2 in package.json or package-lock.json files
• Unexpected SVG files containing complex or obfuscated style elements in application input directories
• Anomalous process behavior or unexpected child processes spawned from Node.js or web application processes
• Unusual network connections originating from applications that process SVG content

Detection Strategies

• Implement dependency scanning tools to identify canvg v.4.0.2 in your software inventory
• Deploy application-level monitoring to detect unusual code execution patterns when processing SVG content
• Use Software Composition Analysis (SCA) tools to flag vulnerable library versions
• Monitor for attempts to upload or process malformed SVG files with suspicious style elements

Monitoring Recommendations

• Enable verbose logging for applications that process SVG files to capture input characteristics
• Monitor npm/yarn audit outputs for known vulnerabilities in the canvg package
• Implement runtime application self-protection (RASP) to detect and block exploitation attempts
• Set up alerts for unusual system calls or process creation events from SVG processing services

How to Mitigate CVE-2025-25977

Immediate Actions Required

• Audit your applications to identify any usage of canvg version 4.0.2
• Update canvg to a patched version as soon as one becomes available from the maintainers
• If upgrading is not immediately possible, restrict or disable SVG processing from untrusted sources
• Implement strict input validation for all SVG content before processing with canvg

Patch Information

At the time of publication, users should monitor the canvg GitHub repository for security updates and patch releases. Check the project's releases page and security advisories for the latest fixed version. Update your package.json to use a patched version once available:

npm update canvg

Verify the installed version does not include v.4.0.2:

npm list canvg

Workarounds

• Implement a content security policy to restrict execution contexts for SVG processing
• Use a sandboxed environment for SVG rendering to limit the impact of potential code execution
• Sanitize SVG content by stripping or validating style elements before passing to canvg
• Consider using alternative SVG processing libraries until a patch is released for canvg

# Example: Check for vulnerable canvg version in your project
npm list canvg | grep "4.0.2"

# Run npm audit to identify security vulnerabilities
npm audit

# If vulnerable, consider removing and finding alternatives temporarily
npm uninstall canvg