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VulnerabilityPublished Updated

CVE-2026-100807: Mozilla Thunderbird · Improper Privilege Management

Affects Mozilla ThunderbirdSource CVE Database V5

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Not known to be exploited · CVSS 8.8 High · fixed in 140.17 : patch Mozilla Thunderbird soon.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score
8.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 14% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 140.17
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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

Affected software

ProductAffectedFixed in
Mozilla ThunderbirdAffected
  • <153.4
  • <157
  • <140.17
Fixed in
  • 153.4
  • 157
  • 140.17

AI-suggested

The vulnerability has been fixed in Thunderbird versions 140.17, 153.4, and 157, and Firefox ESR 140.17, ESR 153.4, and Firefox 157. Users and administrators should update to these fixed versions or later to remediate the issue. No additional mitigations are specified by the vendor.

Description

CVE-2026-100807 is a high-severity privilege escalation vulnerability in the DOM Service Workers component of Mozilla Thunderbird and Firefox. It allows an attacker to escalate privileges, impacting confidentiality, integrity, and availability. The issue has been fixed in Thunderbird versions 140.17, 153.4, and 157, as well as Firefox ESR 140.17, ESR 153.4, and Firefox 157.

References

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