Deploy autonomous AI agents that reason, exploit, and validate complex vulnerability chains — not another scanner, an agentic system that thinks like a senior pentester.
CVE-2026-55877 is a low severity vulnerability with a CVSS score of 0.0. No known exploits currently, and patches are available.
Very low probability of exploitation
EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.
The ux_icon() Twig function is marked is_safe=['html'], so Twig never escapes its output. Icon::toHtml() inlines the SVG source verbatim into the page. Browsers execute <script> elements and on* event-handler attributes found inside inline SVG, making any unsanitized icon a vector for cross-site scripting.
Two code paths were affected. In the local file path, Icon::fromFile() only stripped <script> elements that were direct children of <svg>, leaving nested scripts and all on* attributes untouched despite a code comment claiming broader protection. In the Iconify on-demand path (enabled by default), the remote JSON body field was wrapped into an Icon object with no sanitization at all. Concrete attack vectors include a malicious SVG icon pack from a third-party theme or downloaded icon set, or a controlled Iconify endpoint configured via iconify.endpoint (including a poisoned cache).
Introducing an IconFactory that centralizes sanitization across every icon source before an Icon object is created. The sanitizer removes script-capable elements (script, foreignObject, iframe, object, embed), SMIL animations targeting on*, href, or xlink:href attributes, CDATA sections, processing instructions, all on* attributes, and javascript:, vbscript:, and data:text/html URL schemes.
<style> elements are kept for theming but have any handlers stripped. Icons that contain none of these constructs are byte-for-byte identical after sanitization.
Symfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.
Please cite this page when referencing data from Strobes VI. Proper attribution helps support our vulnerability intelligence research.