Symfony: HtmlSanitizer UrlAttributeSanitizer Misses URL Attributes

Exploitation

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

CVSS 4.0

5.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N · score source

EPSS

• CVE-2026-48761: 0.34% estimated exploitation activity in the next 30 days; percentile 28.04 (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 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…

Published by the source

15 Jun 2026, 16:46 UTC

Last modified by the source

15 Jun 2026, 16:46 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-x5qj-865h-mgvm

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# Patch Next advisory brief: CVE-2026-48761

Advisory: Symfony: HtmlSanitizer UrlAttributeSanitizer Misses URL Attributes
IDs: CVE-2026-48761, GHSA-x5qj-865h-mgvm
Record: https://patchnext.com/advisories/cve-2026-48761 (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 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: symfony/symfony 8.0.13, 7.4.13, 6.4.41; symfony/html-sanitizer 8.0.13, 7.4.13, 6.4.41. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist symfony/symfony: affected >= 6.1.0, < 6.4.41; >= 7.0.0, < 7.4.13; >= 8.0.0, < 8.0.13; fixed in 6.4.41, 8.0.13, 7.4.13
- Packagist symfony/html-sanitizer: affected >= 6.1.0, < 6.4.41; >= 7.0.0, < 7.4.13; >= 8.0.0, < 8.0.13; fixed in 6.4.41, 8.0.13, 7.4.13

## Suggested inspection (read-only)
- Packagist symfony/symfony: check the installed version with your package manager.
- Packagist symfony/html-sanitizer: 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/symfony, symfony/html-sanitizer.
- 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-x5qj-865h-mgvm (GitHub-reviewed advisory GHSA-x5qj-865h-mgvm lists affected ranges: Packagist symfony/html-sanitizer >=6.1.0 =7.0.0 =8.0.0 =6.1.0 =7.0.0 =8.0.0 <8.0.13)

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