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VulnerabilityPublished Updated

CVE-2026-100801: Mozilla Thunderbird · Privilege escalation in the DLL Services component

Affects Mozilla ThunderbirdSource CVE Database V5

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Not known to be exploited · CVSS 8.8 High · fixed in 153.4 : 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.

Thin evidence

One scorer or none
CVSS scores by source
CISA-ADPCVSS 3.18.8
EPSS
0.2% chance of exploitation in 30 days – higher than 20% 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: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

AI-suggested

Apply the official fixes provided by Mozilla by upgrading to Firefox ESR 153.4, Firefox 159, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox ESR 153.6, or Firefox ESR 140.17 as appropriate. These versions contain the patches that remediate this vulnerability. No additional mitigation steps are indicated by the vendor advisory.

Description

Privilege escalation in the DLL Services component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 159, Firefox ESR 153.6, Thunderbird 159, Thunderbird 153.6, Firefox 157, and Firefox ESR 140.17.

References

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