---
id: "CVE-2026-121373"
kind: "vulnerability"
aliases: ["CVE-2026-121373"]
title: "Symfony HtmlSanitizer: meta refresh bypass allows redirects to untrusted sites"
severity: "medium"
cvss: 5.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["html-sanitizer", "package", "php", "symfony"]
not_affected_if: ["meta-tags-not-allowed", "no-user-html"]
published_at: "2026-11-04T13:17:27+00:00"
first_seen_at: "2026-11-04T13:27:01+00:00"
updated_at: "2026-11-04T13:28:13+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121373", "first_seen_at": "2026-11-04T13:27:01+00:00"}]
---

# Symfony HtmlSanitizer: meta refresh bypass allows redirects to untrusted sites

The Symfony HtmlSanitizer component fails to sanitize some meta refresh directives, so attacker-supplied URLs pass through unchanged. An attacker can make a sanitized page redirect a visitor to an untrusted site, bypassing the configured link scheme and host allowlists.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Symfony version with `composer show symfony/html-sanitizer` and compare it with the fixed ranges below.
- Search your code for `HtmlSanitizer` and `allowStaticElements()` to see whether meta tags with http-equiv and content are allowed.

## Fix

- Symfony 6.1.x: move to `6.4.50` or later
- Symfony 7.x: move to `7.4.23` or later
- Symfony 8.x: move to `8.1.11` or later

## Timeline

- 2026-11-04T13:27:01+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121373

## Documents

- [advisory] Vendor advisory: github.com https://github.com/symfony/symfony/security/advisories/GHSA-wm2w-4mgj-vw33
- [fix] Patch: github.com https://github.com/symfony/symfony/commit/2d4c4fe36200858b91132a95076fff3d9de89d26

## From the sources

The Symfony HtmlSanitizer component MetaRefreshAttributeSanitizer, introduced to fix CVE-2026-48761, sanitizes the refresh URL of content attributes of meta tags using a regular expression that is too narrow, allowing sanitization to be bypassed, and resulting in potential URL redirection to untrusted sites in Symfony versions 6.1.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.




The shared declarative refresh steps in the WHATWG HTML Standard require a broader approach: the separator after the time may be ASCII whitespace alone, with no ; or ,, and the url= keyword is optional. Directives the browser honours, but the regular expression misses are returned unchanged, so the attacker URL skips UrlSanitizer entirely and both allowLinkSchemes and allowLinkHosts are defeated for the refresh navigation.




This is reachable under any configuration that allows meta with http-equiv and content, including the documented allowStaticElements() preset.

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