CVE-2026-86853

MEDIUMPre-NVD 4.34.3—
EchelonGraph scoreHIGH confidence

Score 4.3 from GitHub Security Advisory published 2026-09-08. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 4.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
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.

A malicious webpage could repeatedly trigger external URL schemes, causing system prompts or external application launches. This could make Firefox for iOS temporarily unusable until the page is closed. This vulnerability was fixed in Firefox for iOS 155.1.

CVSS v3
4.3
EG Score
4.3(high)
EG Risk
19(Track)
EG Risk 19/100SSVC: 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%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
7%
KEV
Not listed

Published

September 8, 2026

Last Modified

September 8, 2026

Advisory Details (2)

Auto-updated Sep 8, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Firefox for iOS 155.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-89/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=1847631

Vendor Advisories for CVE-2026-86853(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 19× in last 7d / 32× 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. 2026-09-18 20:05 UTCEG score recompute
  2. 2026-09-18 20:05 UTCGHSA enrichment
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-17 20:19 UTCEG score recompute
  5. 2026-09-17 20:19 UTCGHSA enrichment
  6. 2026-09-17 19:32 UTCEPSS rescore
  7. 2026-09-16 18:17 UTCEG score recompute
  8. 2026-09-16 18:17 UTCGHSA enrichment
  9. 2026-09-16 14:09 UTCEPSS rescore
  10. 2026-09-16 05:15 UTCEPSS rescore
  11. 2026-09-15 18:17 UTCEG score recompute
  12. 2026-09-15 18:17 UTCGHSA enrichment
  13. 2026-09-15 03:12 UTCEPSS rescore
  14. 2026-09-15 03:12 UTCEPSS rescore
  15. 2026-09-14 18:21 UTCGHSA enrichment
  16. 2026-09-13 18:37 UTCEG score recompute
  17. 2026-09-13 18:37 UTCGHSA enrichment
  18. 2026-09-12 18:53 UTCEG score recompute
  19. 2026-09-12 18:53 UTCGHSA enrichment
  20. 2026-09-11 19:08 UTCEG score recompute
  21. 2026-09-11 19:08 UTCGHSA enrichment
  22. 2026-09-11 14:53 UTCEPSS rescore
  23. 2026-09-11 14:53 UTCEPSS rescore
  24. 2026-09-10 19:22 UTCEG score recompute
  25. 2026-09-10 19:22 UTCGHSA enrichment
Show 7 more
  1. 2026-09-09 19:33 UTCGHSA enrichment
  2. 2026-09-08 19:49 UTCEG score recompute
  3. 2026-09-08 19:49 UTCGHSA enrichment
  4. 2026-09-08 15:51 UTCEG score recompute▲ 4.30
  5. 2026-09-08 15:49 UTCMITRE cvelistV5CVSS v3 → 4.3 · severity → MEDIUM
  6. 2026-09-08 15:26 UTCEG score recompute
  7. 2026-09-08 15:24 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-86853?
CVE-2026-86853 is a medium vulnerability published on September 8, 2026. A malicious webpage could repeatedly trigger external URL schemes, causing system prompts or external application launches. This could make Firefox for iOS temporarily unusable until the page is closed. This vulnerability was fixed in Firefox for iOS 155.1.
When was CVE-2026-86853 disclosed?
CVE-2026-86853 was first published in the National Vulnerability Database on September 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-86853 actively exploited?
CVE-2026-86853 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 92.8% of all scored CVEs.
What is the CVSS score of CVE-2026-86853?
CVE-2026-86853 has a CVSS v3.1 base score of 4.3 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-86853?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-86853, 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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