GHSA-6V8J-33HC-MV84
Vulnerability from github – Published: 2026-06-19 21:42 – Updated: 2026-06-19 21:42Description
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).
Resolution
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.
Credits
Symfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.
{
"affected": [
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/ux-icons"
},
"ranges": [
{
"events": [
{
"introduced": "2.17.0"
},
{
"fixed": "2.36.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/ux-icons"
},
"ranges": [
{
"events": [
{
"introduced": "3.0.0"
},
{
"fixed": "3.2.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-55877"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-19T21:42:15Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "### Description\n\nThe `ux_icon()` Twig function is marked `is_safe=[\u0027html\u0027]`, so Twig never escapes its output. `Icon::toHtml()` inlines the SVG source verbatim into the page. Browsers execute `\u003cscript\u003e` elements and `on*` event-handler attributes found inside inline SVG, making any unsanitized icon a vector for cross-site scripting.\n\nTwo code paths were affected. In the local file path, `Icon::fromFile()` only stripped `\u003cscript\u003e` elements that were direct children of `\u003csvg\u003e`, 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).\n\n### Resolution\n\nIntroducing 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. \n`\u003cstyle\u003e` elements are kept for theming but have any handlers stripped. Icons that contain none of these constructs are byte-for-byte identical after sanitization. \n\n### Credits\n\nSymfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.",
"id": "GHSA-6v8j-33hc-mv84",
"modified": "2026-06-19T21:42:15Z",
"published": "2026-06-19T21:42:15Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/symfony/ux/security/advisories/GHSA-6v8j-33hc-mv84"
},
{
"type": "WEB",
"url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/ux-icons/CVE-2026-55877.yaml"
},
{
"type": "PACKAGE",
"url": "https://github.com/symfony/ux"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "symfony/ux-icons: XSS via unsanitized SVG content in local files and Iconify on-demand responses"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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