CVE-2022-23638 is a cross-site scripting (XSS) vulnerability identified in the svg-sanitizer library, a PHP-based tool designed to sanitize SVG/XML content. The vulnerability affects all versions of svg-sanitizer prior to 0.15.0. The root cause is improper neutralization of input during web page generation, classified under CWE-79. This means that malicious input embedded within SVG files is not adequately sanitized, allowing attackers to inject and execute arbitrary JavaScript code in the context of a victim's browser. Since svg-sanitizer is commonly used to clean SVG content before rendering it on web applications, this flaw can be exploited when untrusted SVG files are uploaded or processed by applications relying on vulnerable versions of the library. Successful exploitation could lead to session hijacking, credential theft, or other malicious actions performed on behalf of the victim user. The vulnerability does not require authentication or user interaction beyond viewing the malicious SVG content, increasing its risk profile. The issue was publicly disclosed on February 14, 2022, and fixed in version 0.15.0. No known exploits have been reported in the wild, and no workarounds exist aside from upgrading to the patched version. The lack of a CVSS score necessitates an independent severity assessment based on the impact and exploitability factors.

For European organizations, the impact of this vulnerability depends largely on the extent to which svg-sanitizer is integrated into their web applications or services that process SVG content. Organizations that allow user-generated SVG uploads or dynamically render SVGs from external sources are at risk of client-side attacks that can compromise user sessions and data confidentiality. This is particularly critical for sectors such as finance, e-commerce, healthcare, and government services where sensitive data and user trust are paramount. Exploitation could lead to unauthorized access to user accounts, data leakage, or the spread of malware through compromised web interfaces. Additionally, the vulnerability could be leveraged as a foothold for broader attacks within an organization's network if combined with other vulnerabilities. The absence of known exploits suggests limited active targeting so far, but the ease of exploitation and lack of workarounds mean that organizations should prioritize remediation to prevent potential future attacks.

The primary and most effective mitigation is to upgrade all instances of the svg-sanitizer library to version 0.15.0 or later, where the vulnerability is fixed. Organizations should conduct an inventory to identify all applications and services using svg-sanitizer and ensure timely patching. For environments where immediate upgrading is not feasible, implementing strict input validation and sanitization at the application level before passing SVG content to the sanitizer can reduce risk. Additionally, applying Content Security Policy (CSP) headers that restrict script execution and disallow inline scripts can mitigate the impact of XSS attacks. Web application firewalls (WAFs) configured to detect and block malicious SVG payloads may provide temporary protection. Regular security testing, including penetration testing focused on SVG handling, should be conducted to detect residual vulnerabilities. Finally, educating developers about secure handling of SVG content and the risks of client-side injection attacks will help prevent similar issues in the future.