4.3

CVE-2026-100766: mozilla firefox

CVSS: 4.3v3.1MediumAnalyzed
AliasesUBUNTU-CVE-2026-100766DEBIAN-CVE-2026-100766
Published 29-09-2026Last modified 30-09-2026
Open JSON

Vulnerability summary

CVE-2026-100766 is a medium (CVSS 4.3) vulnerability in mozilla firefox. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.4% 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
0.25%
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. 30-09-2026
    Last modifiedVulnerability information updated.

Description

Information disclosure in the Networking: JAR component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.25%

Chance of exploitation in the next 30 days

Percentile

15%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

30-09-202619-10-2026
EPSS score
0.25%

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< 1:140.17.0esr-1~deb12u1 | < 1:140.17.0esr-1~deb13u1 | < 1:153.4.0esr-1
Mozilla2 products
  • firefox< 115.42.0 | ≥ 116.0.0, < 140.17.0 | ≥ 141.0.0, < 153.4.0 | ≥ 154.0.0, < 157.0.0
  • thunderbird< 140.17.0 | ≥ 141.0, < 153.4.0 | ≥ 154.0, < 157.0

3 vendors · 12 products

References

13 links
Show all 13 references