CVE-2025-25977 in canvg
Summary
by MITRE • 03/10/2025
An issue in canvg v.4.0.2 allows an attacker to execute arbitrary code via the Constructor of the class StyleElement.
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Analysis
by VulDB Data Team • 06/02/2025
The vulnerability identified as CVE-2025-25977 resides within the canvg library version 4.0.2, a popular JavaScript library used for rendering svg graphics in web browsers. This library is widely adopted across various web applications and platforms for its ability to convert svg images into canvas elements, making it an essential component in many digital environments. The flaw specifically targets the StyleElement class constructor, which processes styling information within svg documents. When maliciously crafted svg content is processed through this library, the vulnerability creates an execution path that can be exploited by attackers to run arbitrary code within the context of the application using canvg.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the StyleElement constructor. Attackers can craft specially designed svg elements containing malicious javascript code within style attributes or related properties. When the canvg library processes these elements, the constructor fails to properly sanitize or validate the input data, allowing malicious code to be executed during the rendering process. This represents a classic server-side code injection vulnerability that can be classified under CWE-94, which deals with the execution of code due to improper sanitization of input data. The vulnerability is particularly dangerous because it can be exploited through svg files that appear legitimate, making detection and prevention challenging for security systems.
The operational impact of this vulnerability extends beyond simple code execution, as it can lead to complete system compromise when exploited in web applications. Attackers can leverage this vulnerability to perform cross-site scripting attacks, steal user session information, manipulate application data, or even establish persistent backdoors within affected systems. The attack surface is broad since canvg is used in numerous web applications, content management systems, and web-based tools that process svg graphics. This vulnerability aligns with ATT&CK technique T1566, which covers social engineering through malicious file attachments, and T1059, which involves command and script interpreters for execution. The exploitation requires minimal privileges and can be automated, making it particularly attractive to threat actors seeking to compromise web applications at scale.
Organizations using canvg version 4.0.2 should immediately implement mitigations to protect their systems from potential exploitation. The primary recommendation is to upgrade to the latest version of the canvg library where this vulnerability has been addressed through proper input sanitization and validation mechanisms. Security teams should also implement web application firewalls that can detect and block malicious svg content, particularly focusing on style attribute parsing. Additional defensive measures include implementing content security policies that restrict script execution within svg contexts and conducting regular security assessments of svg processing components within web applications. The vulnerability demonstrates the critical importance of input validation in client-side libraries and highlights the need for comprehensive security testing of third-party dependencies. Organizations should also consider implementing runtime monitoring to detect anomalous code execution patterns that might indicate exploitation attempts, as this vulnerability can be used to bypass traditional security controls.