CVE-2026-66843 — 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-2026-66843LOW

rrrene html_sanitize_ex — html_sanitize_ex HTML5 scrubber keeps attacker-supplied `<object>` elements, allowing untrusted content embedding

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   P   N   P   N   N   N    2.3   .0029   21.6     —

AFFECTED
  Product           Versions                                    Fixed
  html_sanitize_ex  0.3.1 –                                     —
  html_sanitize_ex  8976d64ea0b77d26093a94a43ec48a3978e8d028 –  bec27fec4de99e40c68c4285a610e09e791a3eaf

TIMELINE
  Aug 6   Reserved by EEF
  Aug 6   Published (CNA: EEF)
  Aug 18  PATCH SHIPPED — CVE-2026-66843 (rrrene html_sanitize_ex). Fixed in html_sanitize_ex bec27fec4de99e40c68c4285a610e09e791a3eaf.

CWE-829 · CNA: EEF · CVSS v4.0 · 5 references · NVD status: Analyzed

Description

Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an <object> element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase "javascript:", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive. This is not unconditional cross-site scripting. A javascript: URL does not execute through <object data> in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path. 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-2026-66843 (rrrene html_sanitize_ex). Fixed in html_sanitize_ex bec27fec4de99e40c68c4285a610e09e791a3eaf.

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	bec27fec4de99e40c68c4285a610e09e791a3eaf

Weaknesses

CWE-829

References (5)

https://cna.erlef.org/cves/CVE-2026-66843.html [related]
https://github.com/rrrene/html_sanitize_ex/commit/bec27fec4de99e40c68c4285a610e09e791a3eaf [patch]
https://github.com/rrrene/html_sanitize_ex/commit/ce038aa1af5a960d50f8eb5d368cc57bb2b9a9f0 [patch]
https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-xmm9-jc22-rcgj [vendor-advisory, related]
https://osv.dev/vulnerability/EEF-CVE-2026-66843 [related]

Authoritative record: CVE-2026-66843 at cve.org

Vendors: rrrene

Weaknesses: CWE-829

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-66843 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.