VDB-221249 · CVE-2021-43529 · GCVE-0-2021-43529

Mozilla Thunderbird up to 91.2.x SMIME Message heap-based overflow

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.
7.9	$5k-$25k	0.00

Summaryinfo

A vulnerability was found in Mozilla Thunderbird up to 91.2.x. It has been rated as critical. The affected element is an unknown function of the component SMIME Message Handler. The manipulation leads to heap-based overflow. This vulnerability is traded as CVE-2021-43529. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Mozilla Thunderbird up to 91.2.x (Mail Client Software). This issue affects an unknown function of the component SMIME Message Handler. The manipulation with an unknown input leads to a heap-based overflow vulnerability. Using CWE to declare the problem leads to CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Thunderbird versions prior to 91.3.0 are vulnerable to the heap overflow described in CVE-2021-43527 when processing S/MIME messages. Thunderbird versions 91.3.0 and later will not call the vulnerable code when processing S/MIME messages that contain certificates with DER-encoded DSA or RSA-PSS signatures.

The weakness was shared 02/17/2023. The advisory is shared at bugzilla.mozilla.org. The identification of this vulnerability is CVE-2021-43529 since 11/08/2021. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 03/19/2025).

Upgrading to version 91.3.0 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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: 8.0
VulDB Meta Temp Score: 7.9

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 9.8
NVD Vector: 🔍

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Heap-based overflow
CWE: CWE-122 / 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

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: Thunderbird 91.3.0

Timelineinfo

11/08/2021 🔍
02/17/2023 +466 days 🔍
02/17/2023 +0 days 🔍
03/19/2025 +761 days 🔍

Sourcesinfo

Vendor: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2021-43529 (🔍)
GCVE (CVE): GCVE-0-2021-43529
GCVE (VulDB): GCVE-100-221249

Entryinfo

Created: 02/17/2023 07:53
Updated: 03/19/2025 16:37
Changes: 02/17/2023 07:53 (41), 03/19/2025 16:37 (27)
Complete: 🔍
Cache ID: 216::103