CVE-2026-66370 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-66370MEDIUM

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

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   P   N   A   N   N   N    4.8   .0023   13.9     —

AFFECTED
  Product           Versions                                    Fixed
  html_sanitize_ex  0.3.1 –                                     —
  html_sanitize_ex  8976d64ea0b77d26093a94a43ec48a3978e8d028 –  a1e804ed997e780ea71d14393cf2f701330553a6

TIMELINE
  Aug 6   Reserved by EEF
  Aug 6   Published (CNA: EEF)
  Aug 18  PATCH SHIPPED — CVE-2026-66370 (rrrene html_sanitize_ex). Fixed in html_sanitize_ex a1e804ed997e780ea71d14393cf2f701330553a6.

CWE-601 · CNA: EEF · CVSS v4.0 · 5 references · NVD status: Analyzed

Description

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
August 6, 2026	Reserved	Reserved by EEF
August 6, 2026	Published	Published (CNA: EEF)
August 18, 2026	PATCH SHIPPED	PATCH SHIPPED — CVE-2026-66370 (rrrene html_sanitize_ex). Fixed in html_sanitize_ex a1e804ed997e780ea71d14393cf2f701330553a6.

Affected

Affected products and packages — 2 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
rrrene	html_sanitize_ex	—	0.3.1	—
rrrene	html_sanitize_ex	—	8976d64ea0b77d26093a94a43ec48a3978e8d028	a1e804ed997e780ea71d14393cf2f701330553a6

Weaknesses

CWE-601

References (5)

https://cna.erlef.org/cves/CVE-2026-66370.html [related]
https://github.com/rrrene/html_sanitize_ex/commit/21394e758cb0ffe12fb9953c30fdedc6016c8f9e [patch]
https://github.com/rrrene/html_sanitize_ex/commit/a1e804ed997e780ea71d14393cf2f701330553a6 [patch]
https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-w3f9-jjhw-wwvq [vendor-advisory, related]
https://osv.dev/vulnerability/EEF-CVE-2026-66370 [related]

Authoritative record: CVE-2026-66370 at cve.org

Vendors: rrrene

Weaknesses: CWE-601

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-66370 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.