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VulnerabilityPublished Updated

CVE-2026-100766: Information Disclosure

Source GCVE Database

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Authoritative record:CVE-2026-100766· Medium 4.3

Not known to be exploited · CVSS 4.3 Medium · fixed in 153.4 : update Firefox when convenient.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score
4.3Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 16% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 153.4
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

AI-suggested

A fix is available and has been released by Mozilla. Users and administrators should update to Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, or Firefox ESR 140.17 or later to remediate this vulnerability. No additional mitigation steps are required beyond applying the official update.

Description

CVE-2026-100766 is an information disclosure vulnerability in the Networking: JAR component of Firefox. The issue allows unauthorized disclosure of information. This vulnerability has been fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. The CVSS v3.1 base score is 4.3, indicating a medium severity level.

References

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