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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-55877: 0.34% estimated exploitation activity in the next 30 days; percentile 27.27 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description The uxicon() Twig function is marked issafe=['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…

Published by the source

19 Jun 2026, 21:42 UTC

Last modified by the source

19 Jun 2026, 21:42 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6v8j-33hc-mv84

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# Patch Next advisory brief: CVE-2026-55877

Advisory: symfony/ux-icons: XSS via unsanitized SVG content in local files and Iconify on-demand responses
IDs: CVE-2026-55877, GHSA-6v8j-33hc-mv84
Record: https://patchnext.com/advisories/cve-2026-55877 (revision 1, source checked 26 Oct 2026, 14:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: symfony/ux-icons 3.2.0, 2.36.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist symfony/ux-icons: affected >= 2.17.0, < 2.36.1; >= 3.0.0, < 3.2.0; fixed in 2.36.1, 3.2.0

## Suggested inspection (read-only)
- Packagist symfony/ux-icons: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on symfony/ux-icons.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6v8j-33hc-mv84 (GitHub-reviewed advisory GHSA-6v8j-33hc-mv84 lists affected ranges: Packagist symfony/ux-icons >=2.17.0 =3.0.0 <3.2.0)

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