# CVE-2026-121373: Symfony: HtmlSanitizer MetaRefreshAttributeSanitizer Matches Only a Narrow Subset of the Browser Refresh Grammar (Incomplete Fix for CVE-2026-48761)

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: Checkmarx) — https://github.com/symfony/symfony/commit/2d4c4fe36200858b91132a95076fff3d9de89d26

## Affected products and versions

- sensiolabs / symfony (symfony/html-sanitizer): ≥ 6.1; < 6.4.50 (affected, git); ≥ 7; < 7.4.23 (affected, git); ≥ 8; < 8.1.11 (affected, git). Source: CNA: Checkmarx

## Severity and prioritization

- CVSS 4.0: 5.3 (medium); 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; source: CNA: Checkmarx

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-186, CWE-601

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/symfony/symfony/security/advisories/GHSA-wm2w-4mgj-vw33 (CNA: Checkmarx; third-party-advisory)

- https://github.com/symfony/symfony/commit/2d4c4fe36200858b91132a95076fff3d9de89d26 (CNA: Checkmarx; patch)

## Provenance

- CNA: Checkmarx: https://www.cve.org/CVERecord?id=CVE-2026-121373; retrieved 2026-11-04; source updated 2026-11-04

Revision: af88bf48157e5a9c1de066513be66e5fa71c684c34062edea2ab4a23fff6136f

Canonical: https://y2.dev/cve/CVE-2026-121373

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