CVE-2026-55877: Symfony UX Icons cross-site scripting via unsanitized SVG content

CVE-2026-55877 · Severity: medium · CVSS 6.1 · Published 2026-07-08

Symfony UX Icons is a library used to integrate icons into Symfony web applications. A security flaw allows malicious code hidden within SVG icon files or remote icon services to be executed in a user's browser. This could lead to cross-site scripting (XSS) attacks, potentially allowing an attacker to steal user sessions or perform unauthorized actions on behalf of users.

Vendors: Packagist, Symfony.

Quick answers

Is CVE-2026-55877 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55877 being exploited in the wild.
How severe is CVE-2026-55877?
Medium severity, with a CVSS score of 6.1, published 8 July 2026.
Which products and versions are affected?
symfony/ux-icons (Packagist) ECOSYSTEM:introduced=2.17.0,fixed=2.36.1; Symfony UX Icons >= 2.17.0, < 2.36.1; >= 3.0.0, < 3.2.0.
Is there a fix for CVE-2026-55877?
Yes. symfony/ux-icons (Packagist): upgrade to 2.36.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55877 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-55877?
Check whether you run symfony/ux-icons (Packagist) or Symfony UX Icons at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • symfony/ux-icons (Packagist): upgrade to 2.36.1 or later
    composer require symfony/ux-icons:^2.36.1

Technical details

A cross-site scripting (XSS) vulnerability exists in the ux_icon() Twig function of Symfony UX Icons. The function is marked as 'is_safe=html', and the Icon::toHtml() method inlines SVG source code verbatim without adequate sanitization. This allows malicious SVG files (either stored locally or fetched from a remote Iconify endpoint) containing script elements, event handlers (on*), or dangerous URL schemes to execute JavaScript in the context of the user's browser. The issue stems from incomplete sanitization in Icon::fromFile() and a total lack of sanitization for Iconify JSON responses. The fix introduces an IconFactory that centralizes sanitization, stripping dangerous elements like <script>, <foreignObject>, and <iframe before icon creation.

Affected products

  • Symfony ux-icons >= 2.17.0, < 2.36.1; >= 3.0.0, < 3.2.0

Identifiers

  • CVE-2026-55877
  • GHSA-6v8j-33hc-mv84

Timeline

  • 2026-06-19: patched: Fixes released in versions 2.36.1 and 3.2.0
  • 2026-07-08: disclosed: CVE-2026-55877 published

References

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