Symfony UX Icons: Malicious SVG Icons Can Run Scripts in the Page

Published as "symfony/ux-icons XSS via unsanitized SVG content in local files and Iconify on-demand responses"

medium Symfony Symfony UX · Last reviewed Nov 4, 2026

CVE: CVE-2026-55877
GHSA: GHSA-6v8j-33hc-mv84
Packagist: PKSA-2rqz-j593-s85p
Reported: Jun 19, 2026

Lets a malicious icon file or Iconify endpoint run script in visitors' browsers in apps that render icons with ux_icon().

Affected and fixed versions

In symfony/ux-icons. Find the row for the version you run, and update to the release next to it.

If you run	Update to	Support
3.0.0 – 3.1.x	3.2.0	Supported
2.17.0 – 2.36.0	2.36.1	Supported

Upgrade

Run the line for the branch you are on.

composer require symfony/ux-icons:^3.2.0
composer require symfony/ux-icons:^2.36.1

What this means

A malicious SVG icon can run script in your visitors' browsers. This is cross-site scripting (XSS): code from an attacker running as if it came from your site. The ux_icon() Twig function puts the icon's SVG straight into the page without escaping, and the icon wasn't fully cleaned first.

Who is affected

Apps on symfony/ux-icons from 2.17.0 up to (not including) 2.36.1, or 3.x before 3.2.0, that render icons with ux_icon(). The Symfony UX advisory names two ways in:

Local SVG files, such as icons from a third-party theme or a downloaded icon set. Only some <script> elements were stripped, and event handler attributes like onload were kept.
Icons fetched on demand from Iconify, which is on by default. Those weren't cleaned at all, so a malicious or poisoned iconify.endpoint could inject script.

If every icon you use comes from a source you control and trust, the risk is low.

What to do

Update symfony/ux-icons to 3.2.0, or to 2.36.1 on 2.x. The fix cleans every icon, from any source, before it's rendered. It removes scripts, event handlers and dangerous URLs. Icons without any of those come out unchanged.

Reported by Pascal Cescon.

Check your app with an agent

Paste this into a coding agent that can read your project, such as Claude Code, Codex or Amp. It checks your composer.lock against the versions above and tells you what to update, without changing anything.

Check whether the PHP project you have access to is affected by this security advisory, and tell me what to update. Do a read-only check: don't edit files, don't run composer update or composer require, and don't try to reproduce the flaw.

Advisory: Symfony UX Icons: Malicious SVG Icons Can Run Scripts in the Page (CVE-2026-55877, GHSA-6v8j-33hc-mv84)
Details: https://phpnews.net/security/symfony/ghsa-6v8j-33hc-mv84

Affected versions, as Composer constraints:
- symfony/ux-icons: >=2.17.0,<2.36.1|>=3.0.0,<3.2.0

Fixed releases on branches that still get security fixes:
- 3.0.0 – 3.1.x: update to 3.2.0
- 2.17.0 – 2.36.0: update to 2.36.1

1. Find every composer.lock in the project outside vendor/ (a monorepo can have one per app) and read the installed version of each package above. Packages installed as dependencies of other packages count too.
2. Compare each installed version with its constraint: "|" separates alternative ranges, and "," means both bounds apply.
3. For each affected install, read "What this means" at https://phpnews.net/security/symfony/ghsa-6v8j-33hc-mv84 and check whether the project meets the conditions it describes (a feature in use, a config value, a driver). Say which conditions you could check and which you couldn't.
4. Report a table: lock file | package | installed version | affected (yes, no or unknown) | conditions met (yes, no or unknown) | update to | evidence. For each affected package, give the command that would fix it, without running it: composer update <package> --with-dependencies when it is only installed as a dependency of another package, or composer require with the fixed version when composer.json requires it directly. If the installed version is on a branch with no fixed release listed, say it needs a move to a newer branch.

Sources

← All Symfony UX advisories