VDB-398455 · CVE-2026-84971 · Nessus 342821

MongoDB libmongocrypt up to 1.20.3 assertion

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5.3	$0-$5k	0.00

Summaryinfo

A vulnerability, which was classified as problematic, has been found in MongoDB libmongocrypt up to 1.20.3. This affects an unknown part. This manipulation causes input validation. This vulnerability is registered as CVE-2026-84971. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in MongoDB libmongocrypt up to 1.20.3. It has been declared as problematic. Affected by this vulnerability is an unknown functionality. The manipulation with an unknown input leads to a input validation vulnerability. The CWE definition for the vulnerability is CWE-617. The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary. As an impact it is known to affect availability. The summary by CVE is:

Improper handling of an unexpected value size in the decryption path of a client-side encryption library can cause a failed internal check that terminates the process using the library. A party able to place a suitably formed encrypted value where an application will decrypt it, or able to control the responses the application receives, may cause that application to stop running.

It is possible to read the advisory at jira.mongodb.org. This vulnerability is known as CVE-2026-84971 since 09/02/2026. The exploitation appears to be easy. The attack can be launched remotely. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 342821 (Linux Distros Unpatched Vulnerability : CVE-2026-84971), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.20.4 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (342821) and CERT Bund (WID-SEC-2026-3182). Be aware that VulDB is the high quality source for vulnerability data.

Affected

Open Source MongoDB

Productinfo

Type

Database Software

Vendor

MongoDB

Name

libmongocrypt

Version

License

open-source

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 5.4
VulDB Meta Temp Score: 5.3

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

CNA Base Score: 6.5
CNA Vector (mongodb): 🔒

CVSSv2info

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Assertion
CWE: CWE-617
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: 342821
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-84971

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: libmongocrypt 1.20.4

Timelineinfo

09/02/2026 CVE reserved
09/03/2026 +1 days Advisory disclosed
09/03/2026 +0 days VulDB entry created
09/18/2026 +15 days VulDB entry last update

Sourcesinfo

Advisory: jira.mongodb.org
Status: Confirmed

CVE: CVE-2026-84971 (🔒)
GCVE (CVE): GCVE-0-2026-84971
GCVE (VulDB): GCVE-100-398455
CERT Bund: WID-SEC-2026-3182 - MongoDB: Mehrere Schwachstellen

Entryinfo

Created: 09/03/2026 17:24
Updated: 09/18/2026 08:07
Changes: 09/03/2026 17:24 (75), 09/04/2026 21:15 (7), 09/05/2026 00:31 (2), 09/18/2026 08:07 (2)
Complete: 🔍
Cache ID: 216::103