CVE-2026-84137

MEDIUMNVD 4.34.3—
EchelonGraph scoreHIGH confidence

Score 4.3 from GitHub Security Advisory published 2026-09-01. NVD baseline CVSS 4.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
4.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 4.3Exploit: None knownExposed: 0

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

Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.

CVSS v3
4.3
EG Score
4.3(high)
EG Risk
34(Track)
EG Risk 34/100SSVC: 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
Severity43% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
3%
KEV
Not listed

Published

September 1, 2026

Last Modified

September 3, 2026

Advisory Details (5)

Auto-updated Sep 3, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 153.2 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-88/
generic

Security Vulnerabilities fixed in Thunderbird 155 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-86/
generic

Security Vulnerabilities fixed in Firefox ESR 153.2 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-85/
generic

Security Vulnerabilities fixed in Firefox 155 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-82/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2051146

Vendor Advisories for CVE-2026-84137(1)

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

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 18× in last 7d / 52× 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. 2026-09-19 10:45 UTCEG score recompute
  2. 2026-09-19 10:45 UTCGHSA enrichment
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-18 11:47 UTCGHSA enrichment
  5. 2026-09-17 13:07 UTCGHSA enrichment
  6. 2026-09-16 14:27 UTCEG score recompute
  7. 2026-09-16 14:27 UTCGHSA enrichment
  8. 2026-09-16 14:09 UTCEPSS rescore
  9. 2026-09-16 05:15 UTCEPSS rescore
  10. 2026-09-15 15:44 UTCEG score recompute
  11. 2026-09-15 15:44 UTCGHSA enrichment
  12. 2026-09-15 03:12 UTCEPSS rescore
  13. 2026-09-15 03:12 UTCEPSS rescore
  14. 2026-09-14 17:02 UTCGHSA enrichment
  15. 2026-09-13 18:22 UTCEG score recompute
  16. 2026-09-13 18:22 UTCGHSA enrichment
  17. 2026-09-12 19:42 UTCEG score recompute
  18. 2026-09-12 19:42 UTCGHSA enrichment
  19. 2026-09-11 21:01 UTCEG score recompute
  20. 2026-09-11 21:01 UTCGHSA enrichment
  21. 2026-09-11 14:53 UTCEPSS rescore
  22. 2026-09-11 14:53 UTCEPSS rescore
  23. 2026-09-10 22:21 UTCEG score recompute
  24. 2026-09-10 22:21 UTCGHSA enrichment
  25. 2026-09-09 23:39 UTCGHSA enrichment
Show 27 more
  1. 2026-09-08 23:25 UTCEG score recompute
  2. 2026-09-08 23:25 UTCGHSA enrichment
  3. 2026-09-08 22:01 UTCEPSS rescore
  4. 2026-09-07 14:55 UTCGHSA enrichment
  5. 2026-09-06 14:49 UTCEG score recompute
  6. 2026-09-06 14:49 UTCGHSA enrichment
  7. 2026-09-06 13:48 UTCEPSS rescore
  8. 2026-09-05 16:08 UTCGHSA enrichment
  9. 2026-09-04 17:28 UTCEG score recompute
  10. 2026-09-04 17:28 UTCGHSA enrichment
  11. 2026-09-04 05:07 UTCEPSS rescore
  12. 2026-09-03 18:46 UTCEG score recompute
  13. 2026-09-03 18:45 UTCGHSA enrichment
  14. 2026-09-03 17:35 UTCEG score recompute
  15. 2026-09-03 17:35 UTCGHSA enrichment
  16. 2026-09-03 16:54 UTCEG score recompute▲ 4.30
  17. 2026-09-03 16:54 UTCGHSA enrichment
  18. 2026-09-03 16:53 UTCNVD updateCVSS v3 → 4.3 · severity → MEDIUM
  19. 2026-09-02 14:12 UTCEPSS rescore
  20. 2026-09-01 22:19 UTCGHSA enrichment
  21. 2026-09-01 22:18 UTCNVD update
  22. 2026-09-01 21:43 UTCGHSA enrichment
  23. 2026-09-01 21:42 UTCMITRE cvelistV5
  24. 2026-09-01 21:08 UTCGHSA enrichment
  25. 2026-09-01 13:35 UTCNVD update
  26. 2026-09-01 12:44 UTCEG score recompute
  27. 2026-09-01 12:41 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-84137?
CVE-2026-84137 is a medium vulnerability published on September 1, 2026. Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
When was CVE-2026-84137 disclosed?
CVE-2026-84137 was first published in the National Vulnerability Database on September 1, 2026, with the most recent update on September 3, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-84137 actively exploited?
CVE-2026-84137 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 97.1% of all scored CVEs.
What is the CVSS score of CVE-2026-84137?
CVE-2026-84137 has a CVSS v3 base score of 4.3 (NVD).
How do I remediate CVE-2026-84137?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-84137, 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

Explore the affected products and dependency analysis for CVE-2026-84137

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