CVE-2026-55877

Received Received - Intake

Stored XSS in Symfony UX JavaScript Ecosystem

Publication date: 2026-07-08

Last updated on: 2026-07-08

Assigner: GitHub, Inc.

Description

Symfony UX is a JavaScript ecosystem for Symfony. From 2.17.0 before 2.36.1 and from 3.0.0 before 3.2.0, the ux_icon() Twig function is marked is_safe=['html'] and Icon::toHtml() inlines SVG source verbatim, allowing unsanitized local SVG files or Iconify on-demand JSON body responses containing nested script elements, on* event handlers, or dangerous URL schemes to execute cross-site scripting. This issue is fixed in versions 2.36.1 and 3.2.0.

CVSS Scores

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Meta Information

Published

2026-07-08

Last Modified

2026-07-08

Generated

2026-07-09

AI Q&A

2026-07-09

EPSS Evaluated

N/A

NVD

CVE-2026-55877

Affected Vendors & Products

Vendor	Product	Version / Range
symfony	ux	From 2.17.0 (inc) to 2.36.1 (exc)
symfony	ux	From 3.0.0 (inc) to 3.2.0 (exc)
symfony	ux	2.36.1
symfony	ux	3.2.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-79	The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

Attack-Flow Graph

Executive Summary

This vulnerability exists in Symfony UX, a JavaScript ecosystem for Symfony, specifically in the ux_icon() Twig function and Icon::toHtml() method. These functions inline SVG source code verbatim and mark the output as safe HTML without sanitization. This allows malicious SVG files or JSON responses containing nested script elements, event handlers, or dangerous URL schemes to execute cross-site scripting (XSS) attacks.

Impact Analysis

The vulnerability can lead to cross-site scripting (XSS) attacks, where an attacker can execute arbitrary scripts in the context of the affected web application. This can result in the theft of user credentials, session hijacking, defacement of the website, or the execution of malicious actions on behalf of the user.

Mitigation Strategies

To mitigate this vulnerability, you should upgrade Symfony UX to version 2.36.1 or later if you are using the 2.x series, or to version 3.2.0 or later if you are using the 3.x series.

These versions fix the issue where the ux_icon() Twig function and Icon::toHtml() inline SVG source verbatim, which could allow cross-site scripting via unsanitized local SVG files or Iconify JSON responses.

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