9.6

CVE-2026-100828: mozilla firefox Protection Mechanism Failure

CVSS: 9.6v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-100828DEBIAN-CVE-2026-100828
Published 29-09-2026Last modified 01-10-2026
Open JSON

Vulnerability summary

CVE-2026-100828 is a critical (CVSS 9.6) Protection Mechanism Failure vulnerability in mozilla firefox. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 13.9% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.6/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.24%
0%100%
Low · Change unavailable
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 10 · Related 8
MGASA-2026-0491MGASA-2026-0492OPENSUSE-SU-2026:11917-1OPENSUSE-SU-2026:12097-1OPENSUSE-SU-2026:12098-1OPENSUSE-SU-2026:21980-1

Timeline

  1. 29-09-2026
    PublishedVulnerability first disclosed.
  2. 01-10-2026
    Last modifiedVulnerability information updated.

Description

Mitigation bypass in the Bookmarks & History component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.24%

Chance of exploitation in the next 30 days

Percentile

14%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

30-09-202619-10-2026
EPSS score
0.24%

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)
Debian2 products
  • firefox-esr< 153.4.0esr-1~deb12u1 | < 153.4.0esr-1~deb13u1 | < 153.4.0esr-1
  • thunderbird< 1:153.4.0esr-1
Mozilla2 products

3 vendors · 12 products

References

10 links