VDB-172043 · CVE-2021-23987 · Nessus 296367

Mozilla Firefox/Firefox ESR/Thunderbird memory corruption

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.
7.4	$0-$5k	0.00

Summaryinfo

A vulnerability marked as critical has been reported in Mozilla Firefox, Firefox ESR and Thunderbird. This vulnerability affects unknown code. The manipulation leads to memory corruption. This vulnerability is listed as CVE-2021-23987. The attack may be initiated remotely. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Mozilla Firefox, Firefox ESR and Thunderbird (Web Browser) (the affected version is unknown). It has been rated as critical. This issue affects an unknown code. The manipulation with an unknown input leads to a memory corruption vulnerability. Using CWE to declare the problem leads to CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. Impacted is confidentiality, integrity, and availability.

The weakness was presented 03/31/2021. It is possible to read the advisory at bugzilla.mozilla.org. The identification of this vulnerability is CVE-2021-23987. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 01/25/2026).

The vulnerability scanner Nessus provides a plugin with the ID 296367 (MiracleLinux 4 : thunderbird-78.9.0-3.0.1.AXS4 (AXSA:2021-1624:05)), which helps to determine the existence of the flaw in a target environment.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (296367). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

Web Browser

Vendor

Mozilla

Name

License

open-source

Website

Vendor: https://www.mozilla.org/
Product: https://www.mozilla.org/en-US/firefox/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.6
VulDB Meta Temp Score: 7.4

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

NVD Base Score: 8.8
NVD 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: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Memory corruption
CWE: 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: 296367
Nessus Name: MiracleLinux 4 : thunderbird-78.9.0-3.0.1.AXS4 (AXSA:2021-1624:05)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Timelineinfo

01/13/2021 🔍
03/31/2021 +76 days 🔍
03/31/2021 +0 days 🔍
01/25/2026 +1761 days 🔍

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2021-23987 (🔍)
GCVE (CVE): GCVE-0-2021-23987
GCVE (VulDB): GCVE-100-172043

Entryinfo

Created: 03/31/2021 22:04
Updated: 01/25/2026 15:48
Changes: 03/31/2021 22:04 (37), 04/07/2021 13:21 (5), 04/07/2021 13:26 (18), 01/25/2026 15:48 (17)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.