4.3

CVE-2026-86853: mozilla firefox_mobile

CVSS: 4.3v3.1MediumAnalyzed
Published 08-09-2026Last modified 08-09-2026
Open JSON

Vulnerability summary

CVE-2026-86853 is a medium (CVSS 4.3) vulnerability in mozilla firefox_mobile. EPSS estimates a 0.28% chance of exploitation in the next 30 days, higher than 19.1% of scored vulnerabilities.

Overall risk
17/100
0100
Low · default modelHow is this calculated?
CVSS score
4.3/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.28%
0%100%
Low · +0.10 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 08-09-2026
    PublishedVulnerability first disclosed.
  2. 08-09-2026
    Last modifiedVulnerability information updated.

Description

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 metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.28%

Chance of exploitation in the next 30 days

Percentile

19%

Versus all other CVEs

30-day change

+0.10 pp

From 0.17% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.28%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Mozilla1 product

1 vendor · 1 product

References

2 links