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UK Cyber Defence
VulnerabilityAnalyzed

CVE-2026-100766

Information disclosure in the Networking: JAR component.

MEDIUM 4.3EPSS 0.25%

Does this matter?

Lower severity and a low EPSS score (0.25%). Track it; it rarely justifies an emergency change on its own.

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 3.1
4.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
EPSS
0.25% probability · 16th percentile
Public exploits
None in Exploit-DB
CISA KEV
Not listed
Weakness
CWE-200
Affected
mozilla/firefox · mozilla/thunderbird
Source
security@mozilla.org
EPSS trend
0%3%5%30 September 2026: 0.24%26 October 2026: 0.25%30 September 202626 October 2026

EPSS moved from 0.2% on 30 September 2026 to 0.3% on 26 October 2026.

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.