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TI-2026-85060 Aliases CVE-2026-121373

Symfony HtmlSanitizer meta refresh filter bypass enables redirects

Priority LOW 25CWE-186Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Passive
Attack complexity
Low
Attack requirements
None
Impact type
Spoofing
Confidentiality · integrity · availability
None · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-601.

Summary

The Symfony HtmlSanitizer component from 6.1.0 before 6.4.50, from 7.0.0 before 7.4.23 and from 8.0.0 before 8.1.11 uses an overly restrictive regular expression in MetaRefreshAttributeSanitizer (CWE-186). The pattern misses meta refresh directives that browsers accept, so the refresh URL skips URL sanitization and the allowLinkSchemes and allowLinkHosts checks. A remote attacker can supply content that redirects a user to an untrusted site.

Written with Claude Haiku 5.5 from the sources below · 2026-11-04

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00482 41st percentileScored 2026-11-07
Fix Fixed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

No affected products listed by the sources yet.

Remediation

Upgrade Symfony to 6.4.50, 7.4.23 or 8.1.11, the fixed versions for the 6.x, 7.x and 8.x branches.

Written with Claude Haiku 5.5 from the sources below · 2026-11-04

Timeline

  1. 2026-11-04 Threatist record created from CVE-2026-121373
  2. 2026-11-04 Affected versions changed · CNA
  3. 2026-11-04 CISA SSVC decision points changed

References

Patch 1

Advisory 1

  • TI-2019-13616 An issue was discovered in Symfony 3.4.0 through 3.4.34, 4.2.0 through 4.2.11, and 4.3.0… CVSS 3.1CRITICAL 9.8
  • TI-2018-10604 An issue was discovered in Http Foundation in Symfony 2.7.0 through 2.7.48, 2.8.0 through… CVSS 3.1MEDIUM 6.5
  • TI-2019-08131 In Symfony before 2.7.51, 2.8.x before 2.8.50, 3.x before 3.4.26, 4.x before 4.1.12, and… CVSS 3.1CRITICAL 9.8
  • TI-2016-02159 Symfony before 2.8.6 and 3.x before 3.0.6 allows remote attackers to bypass… CVSS 3.0CRITICAL 9.8
  • TI-2019-08459 An issue was discovered in Symfony before 4.2.12 and 4.3.x before 4.3.8. CVSS 3.1CRITICAL 9.8
  • TI-2018-08136 An issue was discovered in the Ldap component in Symfony 2.8.x before 2.8.37, 3.3.x… CVSS 3.0CRITICAL 9.8
See all 107 →

Sources

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