9.1

CVE-2026-74938: mozilla firefox Protection Mechanism Failure

CVSS: 9.1v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-74938CGA-483x-gr3g-rv92CGA-7m32-hh7v-8c66
Published 18-08-2026Last modified 18-08-2026
Open JSON

Vulnerability summary

CVE-2026-74938 is a critical (CVSS 9.1) Protection Mechanism Failure vulnerability in mozilla firefox. EPSS estimates a 0.44% chance of exploitation in the next 30 days, higher than 37% 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
0.44%
0%100%
Low · +0.12 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 12
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. 18-08-2026
    Last modifiedVulnerability information updated.

Description

Mitigation bypass in the JavaScript: GC 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

0.44%

Chance of exploitation in the next 30 days

Percentile

37%

Versus all other CVEs

30-day change

+0.12 pp

From 0.32% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.44%

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)
Chainguard3 products
  • firefox< 154.0-r0
  • firefox-docker-selenium-compat< 154.0-r0
  • firefox-esr-140All versions (No fix recorded)
Mozilla2 products
Wolfi2 products
  • firefox< 154.0-r0
  • firefox-docker-selenium-compat< 154.0-r0

4 vendors · 15 products

References

8 links