Executive brief
Symfony UX Icons is a library used to integrate icons into Symfony web applications. A security flaw allows malicious code hidden within SVG icon files or remote icon services to be executed in a user's browser. This could lead to cross-site scripting (XSS) attacks, potentially allowing an attacker to steal user sessions or perform unauthorized actions on behalf of users.
Technical details
A cross-site scripting (XSS) vulnerability exists in the ux_icon() Twig function of Symfony UX Icons. The function is marked as 'is_safe=html', and the Icon::toHtml() method inlines SVG source code verbatim without adequate sanitization. This allows malicious SVG files (either stored locally or fetched from a remote Iconify endpoint) containing script elements, event handlers (on*), or dangerous URL schemes to execute JavaScript in the context of the user's browser. The issue stems from incomplete sanitization in Icon::fromFile() and a total lack of sanitization for Iconify JSON responses. The fix introduces an IconFactory that centralizes sanitization, stripping dangerous elements like <script>, <foreignObject>, and <iframe before icon creation.
Affected products
- Symfony ux-icons >= 2.17.0, < 2.36.1; >= 3.0.0, < 3.2.0
Timeline
- 2026-06-19: patched: Fixes released in versions 2.36.1 and 3.2.0
- 2026-07-08: disclosed: CVE-2026-55877 published