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TI-2026-47137 Aliases CVE-2026-66370GHSA-r8xc-fmjg-37c5

html_sanitize_ex HTML5 scrubber keeps attacker-supplied form-association attributes, allowing form hijacking

Priority LOW 22CWE-601Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Active
Attack complexity
Low
Attack requirements
Present
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

URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the form and formaction attributes on an <input> element in sanitized HTML. HTML's form attribute associates an input with any form on the page by its id even when the input sits outside that form, and formaction on a submit control overrides the owning form's action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing. No script executes. The scrubber allows neither form nor button, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an id. This issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00403 34th percentileScored 2026-11-07
Fix Fixed html_sanitize_ex (rrrene): 1.4.5, 1.5.3

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

VendorProductAffected versionsFixed inStatusSource
rrrenehtml_sanitize_ex0.3.1 to before 1.4.5; 1.5.0-rc.0 to before 1.5.31.4.5, 1.5.3Patch availableCNA
  • html_sanitize_ex Vendorrrrene Affected 0.3.1 to before 1.4.5; 1.5.0-rc.0 to before 1.5.3 Fixed in 1.4.5, 1.5.3 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:rrrene:htmlsanitizeex:*:*:*:*:*:*:*:*0.3.1 to before 1.5.3Vulnerablerrrene
  • cpe:2.3:a:rrrene:htmlsanitizeex:*:*:*:*:*:*:*:* Versions 0.3.1 to before 1.5.3 Vulnerable ·rrrene

Remediation

  • Fix · CNA html_sanitize_ex (rrrene) Fixed in 1.4.5, 1.5.3

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    rrrene html_sanitize_ex 1.4.5, 1.5.3

    5 records Highest priority Priority LOW 5 LOW

    Other records, highest priority first

    • TI-2026-48335 Quadratic sibling re-flattening in the html_sanitize_ex traversal engine allows CPU-exhaustion denial of servicePriority LOW 37
    • TI-2026-48334 Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of servicePriority LOW 37
    • TI-2026-47464 html_sanitize_ex HTML5 scrubber keeps attacker-supplied `<object>` elements, allowing untrusted content embeddingPriority LOW 13
    Show all 5 records →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-66370
  2. 2026-10-03 Alias added: GHSA-r8xc-fmjg-37c5

References

Patch 4

Advisory 1

  • TI-2026-48335 Quadratic sibling re-flattening in the html_sanitize_ex traversal engine allows CPU-exhaustion denial of service CVSS 4.0HIGH 8.2
  • TI-2026-48334 Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of service CVSS 4.0HIGH 8.2
  • TI-2026-47464 html_sanitize_ex HTML5 scrubber keeps attacker-supplied `<object>` elements, allowing untrusted content embedding CVSS 4.0LOW 2.3
  • TI-2026-47457 html_sanitize_ex HTML5 scrubber keeps attacker-supplied meta refresh, allowing forced cross-origin redirection CVSS 4.0LOW 2.3
  • TI-2026-48333 CSS sanitizer allowlist bypass in html_sanitize_ex via non-declaration input CVSS 4.0LOW 2.3

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences