CVE-2026-66843

MEDIUMNVD 6.16.1—
EchelonGraph scoreHIGH confidence

Score 6.1 from GitHub Security Advisory (severity: LOW) published 2026-08-06. NVD baseline CVSS 6.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.1Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 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 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.

CVSS v3
6.1
EG Score
6.1(high)
EG Risk
28(Track)
EG Risk 28/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity61% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
22%
KEV
Not listed

Published

August 6, 2026

Last Modified

August 19, 2026

Advisory Details (3)

Auto-updated Aug 11, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
generic

OSV - Open Source Vulnerabilities

https://osv.dev/vulnerability/EEF-CVE-2026-66843
github_commit

commit bec27fec4de9 (rrrene/html_sanitize_ex)

Fix landed in rrrene/html_sanitize_ex commit bec27fec4de9 — awaiting tagged release

https://github.com/rrrene/html_sanitize_ex/commit/bec27fec4de99e40c68c4285a610e09e791a3eaf
generic

CVE-2026-66843

https://cna.erlef.org/cves/CVE-2026-66843.html

Vendor Advisories for CVE-2026-66843(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Hex(1)
PackageVulnerable rangeFixed inDependents
html_sanitize_ex0.3.1 ... 1.5.2 (21 versions)1.5.3—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 21× in last 7d / 38× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-20 12:28 UTCEG score recompute
  2. 2026-08-20 12:28 UTCGHSA enrichment
  3. 2026-08-19 17:04 UTCEPSS rescore
  4. 2026-08-19 12:25 UTCGHSA enrichment
  5. 2026-08-19 12:00 UTCEG score recompute
  6. 2026-08-19 12:00 UTCGHSA enrichment
  7. 2026-08-18 15:42 UTCEG score recompute
  8. 2026-08-18 15:42 UTCGHSA enrichment
  9. 2026-08-18 13:48 UTCEPSS rescore
  10. 2026-08-17 14:09 UTCEG score recompute
  11. 2026-08-17 14:09 UTCGHSA enrichment
  12. 2026-08-17 13:47 UTCEPSS rescore
  13. 2026-08-16 14:56 UTCEPSS rescore
  14. 2026-08-16 14:07 UTCEG score recompute
  15. 2026-08-16 14:07 UTCGHSA enrichment
  16. 2026-08-15 14:04 UTCEG score recompute
  17. 2026-08-15 14:04 UTCGHSA enrichment
  18. 2026-08-15 01:30 UTCEPSS rescore
  19. 2026-08-14 14:01 UTCEG score recompute
  20. 2026-08-14 14:01 UTCGHSA enrichment
  21. 2026-08-13 22:00 UTCEPSS rescore
  22. 2026-08-13 13:58 UTCGHSA enrichment
  23. 2026-08-12 13:56 UTCEG score recompute
  24. 2026-08-12 13:56 UTCGHSA enrichment
  25. 2026-08-12 13:51 UTCEPSS rescore
Show 13 more
  1. 2026-08-11 13:53 UTCEG score recompute▲ 3.80
  2. 2026-08-11 13:53 UTCGHSA enrichment
  3. 2026-08-11 13:52 UTCNVD updateCVSS v3 → 6.1 · severity → MEDIUM
  4. 2026-08-11 00:00 UTCEPSS rescore
  5. 2026-08-10 14:45 UTCEG score recompute
  6. 2026-08-10 14:45 UTCGHSA enrichment
  7. 2026-08-09 13:47 UTCEPSS rescore
  8. 2026-08-08 16:37 UTCEPSS rescore
  9. 2026-08-07 13:51 UTCGHSA enrichment
  10. 2026-08-06 22:38 UTCGHSA enrichment
  11. 2026-08-06 16:32 UTCEG score recompute
  12. 2026-08-06 15:31 UTCEG score recompute
  13. 2026-08-06 15:31 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-66843?
CVE-2026-66843 is a medium vulnerability published on August 6, 2026. Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene htmlsanitizeex 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…
When was CVE-2026-66843 disclosed?
CVE-2026-66843 was first published in the National Vulnerability Database on August 6, 2026, with the most recent update on August 19, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66843 actively exploited?
CVE-2026-66843 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 78.4% of all scored CVEs.
What is the CVSS score of CVE-2026-66843?
CVE-2026-66843 has a CVSS v3 base score of 6.1 (NVD).
How do I remediate CVE-2026-66843?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66843, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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