Detections
Analytics

Mozilla Thunderbird < 155.0

critical Nessus Plugin ID 342256

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Synopsis

A mail client installed on the remote Windows host is affected by multiple vulnerabilities.

Description

The version of Thunderbird installed on the remote Windows host is prior to 155.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-86 advisory.

 - Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. (CVE-2026-84143, CVE-2026-84145)

 - Triggering an error condition in certain MIME bodies would cause uninitialized memory to be used.
 (CVE-2026-84639)

 - A maliciously constructed mail header could lead to a one byte read past the end of a buffer.
 (CVE-2026-84640)

 - A malicious IMAP server can trigger use-after-free and heap-memory disclosure by sending a crafted ID response. Heap contents can ultimately be persisted to prefs.js. (CVE-2026-84641)

 - The values of the mail.allowedattachmenthostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. (CVE-2026-84642)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Upgrade to Mozilla Thunderbird version 155.0 or later.

See Also

https://www.mozilla.org/en-US/security/advisories/mfsa2026-86/

Plugin Details

Severity: Critical

ID: 342256

File Name: mozilla_thunderbird_155_0.nasl

Version: 1.6

Type: Local

Agent: windows

Family: Windows

Published: 9/1/2026

Updated: 10/21/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5

Percentile: 93.42

CVSS v2

Risk Factor: Critical

Base Score: 10

Temporal Score: 7.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C

CVSS Score Source: CVE-2026-84143

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 8.8

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:mozilla:thunderbird

Required KB Items: installed_sw/Mozilla Thunderbird

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 9/1/2026

Vulnerability Publication Date: 9/1/2026

Reference Information

CVE: CVE-2026-84118, CVE-2026-84119, CVE-2026-84120, CVE-2026-84121, CVE-2026-84122, CVE-2026-84123, CVE-2026-84124, CVE-2026-84125, CVE-2026-84126, CVE-2026-84128, CVE-2026-84129, CVE-2026-84130, CVE-2026-84131, CVE-2026-84132, CVE-2026-84133, CVE-2026-84134, CVE-2026-84136, CVE-2026-84137, CVE-2026-84138, CVE-2026-84139, CVE-2026-84140, CVE-2026-84141, CVE-2026-84142, CVE-2026-84143, CVE-2026-84144, CVE-2026-84145, CVE-2026-84639, CVE-2026-84640, CVE-2026-84641, CVE-2026-84642

IAVA: 2026-A-0929