What is GHSA-x5qj-865h-mgvm?

GHSA-x5qj-865h-mgvm is a security advisory published by GitHub Security Advisories with Medium severity. Symfony: HtmlSanitizer UrlAttributeSanitizer Misses URL Attributes

Which CVE IDs does GHSA-x5qj-865h-mgvm cover?

GHSA-x5qj-865h-mgvm covers the following CVE IDs: CVE-2026-48761. Each CVE has its own detail page on EchelonGraph Pulse with the synthesized EG score.

Which products are affected by GHSA-x5qj-865h-mgvm?

GHSA-x5qj-865h-mgvm affects 6 products, including: composer/symfony/html-sanitizer:\u003e= 6.1.0, \u003c 6.4.41; composer/symfony/html-sanitizer:\u003e= 7.0.0, \u003c 7.4.13; composer/symfony/html-sanitizer:\u003e= 8.0.0, \u003c 8.0.13; composer/symfony/symfony:\u003e= 6.1.0, \u003c 6.4.41; composer/symfony/symfony:\u003e= 7.0.0, \u003c 7.4.13; and others — see the full list on the advisory page.

GHSA-x5qj-865h-mgvmMedium

Symfony: HtmlSanitizer UrlAttributeSanitizer Misses URL Attributes

Vendor

GitHub Security Advisories

Published

June 15, 2026

Last Modified

June 15, 2026

🔗 CVE IDs covered (1)

CVE-2026-48761 →

📋 Description

Description

Symfony\Component\HtmlSanitizer\Visitor\AttributeSanitizer\UrlAttributeSanitizer::getSupportedAttributes() enumerates the attribute names whose values are scrubbed through UrlSanitizer::sanitize() (scheme and host allow-lists, javascript: rejection, BiDi check, etc.). The list is ['src', 'href', 'lowsrc', 'background', 'ping', 'action', 'formaction', 'poster', 'cite']. Other URL-bearing attributes are absent: <object data=…>, <applet codebase=…>, <applet archive=…> and <object archive=…>, <iframe longdesc=…> and <img longdesc=…>. When an integrator opts these elements/attributes in via allowElement('object', ['data']), allowElement('applet', ['codebase']), etc., or via allowAttribute(), no URL sanitization runs: data="javascript:alert(1)" and similar payloads ship through unchanged into the output, enabling stored XSS.

<meta http-equiv="refresh" content="0; url=…"> is the same class of bug routed differently: the URL is embedded inside a multi-field content attribute that the per-attribute sanitizer cannot detect from the attribute name alone. Integrators who enable <meta> with the content attribute (e.g. via allowStaticElements()) see content="0; url=javascript:alert(1)" pass through, producing a refresh-driven navigation to a javascript: URL.

Default configurations are not affected: <object>, <applet> and <iframe> are not in W3CReference::BODY_ELEMENTS and <meta> requires an explicit opt-in to <head> context. The vulnerability surface is integrators who explicitly allow any of those elements together with the listed URL-bearing attributes.

Resolution

UrlAttributeSanitizer now also routes data, codebase, archive and longdesc through UrlSanitizer::sanitize(). A new MetaRefreshAttributeSanitizer registered as a default attribute sanitizer detects the <delay>; url=<url> syntax inside <meta content>, sanitizes the embedded URL, and drops the attribute if the URL is rejected; non-refresh meta content values are passed through unchanged.

The patches for this issue are available here for branch 6.4 (and forward-ported to 7.4, 8.0 and 8.1).

Credits

Symfony would like to thank Scott Arciszewski (Trail of Bits) for reporting the issue and Nicolas Grekas for providing the fix.

🎯 Affected products6

composer/symfony/html-sanitizer:>= 6.1.0, < 6.4.41
composer/symfony/html-sanitizer:>= 7.0.0, < 7.4.13
composer/symfony/html-sanitizer:>= 8.0.0, < 8.0.13
composer/symfony/symfony:>= 6.1.0, < 6.4.41
composer/symfony/symfony:>= 7.0.0, < 7.4.13
composer/symfony/symfony:>= 8.0.0, < 8.0.13