9.1

CVE-2026-74986: mozilla firefox

CVSS: 9.1v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-74986
Published 18-08-2026Last modified 20-08-2026
Open JSON

Vulnerability summary

CVE-2026-74986 is a critical (CVSS 9.1) vulnerability in mozilla firefox. EPSS estimates a 0.56% chance of exploitation in the next 30 days, higher than 45.1% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.1/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.56%
0%100%
Low · +0.23 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 13 · Related 11
MGASA-2026-0345MGASA-2026-0346OPENSUSE-SU-2026:11546-1OPENSUSE-SU-2026:11580-1OPENSUSE-SU-2026:12098-1OPENSUSE-SU-2026:21713-1

Timeline

  1. 18-08-2026
    PublishedVulnerability first disclosed.
  2. 20-08-2026
    Last modifiedVulnerability information updated.

Description

Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.56%

Chance of exploitation in the next 30 days

Percentile

45%

Versus all other CVEs

30-day change

+0.23 pp

From 0.32% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.56%

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

Ubuntu8 products
  • mozjs102All versions (No fix recorded)
  • mozjs115All versions (No fix recorded)
  • mozjs38All versions (No fix recorded)
  • mozjs52All versions (No fix recorded)
  • mozjs68All versions (No fix recorded)
Mozilla2 products

2 vendors · 10 products

References

8 links