VDB-352890 · CVE-2026-4371 · Nessus 303506

Mozilla Thunderbird up to 140.8/148 Email out-of-bounds

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.7	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Mozilla Thunderbird up to 140.8/148. It has been declared as problematic. Affected is an unknown function of the component Email Handler. The manipulation results in out-of-bounds. This vulnerability is known as CVE-2026-4371. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in Mozilla Thunderbird up to 140.8/148. Affected is some unknown processing of the component Email Handler. The manipulation with an unknown input leads to a out-of-bounds vulnerability. CWE is classifying the issue as CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. This is going to have an impact on confidentiality. CVE summarizes:

A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability affects Thunderbird < 149 and Thunderbird < 140.9.

The advisory is available at bugzilla.mozilla.org. This vulnerability is traded as CVE-2026-4371 since 03/18/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 04/15/2026).

The vulnerability scanner Nessus provides a plugin with the ID 303506 (Mozilla Thunderbird < 149.0), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 140.9 or 149 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (303506) and CERT Bund (WID-SEC-2026-0850). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

Debian Linux
Amazon Linux 2
Red Hat Enterprise Linux
SUSE Linux
Oracle Linux
SUSE openSUSE
RESF Rocky Linux
Mozilla Firefox
Mozilla Firefox ESR
Mozilla Thunderbird

Productinfo

Type

Mail Client Software

Vendor

Mozilla

Name

Thunderbird

Version

License

open-source

Website

Vendor: https://www.mozilla.org/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.8
VulDB Meta Temp Score: 5.7

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

ADP CISA Base Score: 7.4
ADP CISA Vector: 🔒

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Out-of-bounds
CWE: CWE-125 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 303506
Nessus Name: Mozilla Thunderbird < 149.0

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Thunderbird 140.9/149

Timelineinfo

03/18/2026 CVE reserved
03/25/2026 +7 days Advisory disclosed
03/25/2026 +0 days VulDB entry created
04/15/2026 +21 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-4371 (🔒)
GCVE (CVE): GCVE-0-2026-4371
GCVE (VulDB): GCVE-100-352890
CERT Bund: WID-SEC-2026-0850 - Mozilla Firefox und Mozilla Thunderbird: Mehrere Schwachstellen

Entryinfo

Created: 03/25/2026 07:22
Updated: 04/15/2026 13:26
Changes: 03/25/2026 07:22 (56), 03/25/2026 08:22 (2), 03/29/2026 16:06 (12), 04/14/2026 09:39 (7), 04/15/2026 13:26 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.