VDB-210732 · CVE-2021-36369 · Nessus 216761

Dropbear up to 2020.81 Non-RFC-compliant Check improper authentication

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.
6.7	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Dropbear up to 2020.81 and classified as critical. Impacted is an unknown function of the component Non-RFC-compliant Check. The manipulation results in improper authentication. This vulnerability is reported as CVE-2021-36369. No exploit exists. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability was found in Dropbear up to 2020.81 (SSH Server Software). It has been classified as critical. Affected is an unknown code of the component Non-RFC-compliant Check. The manipulation with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

An issue was discovered in Dropbear through 2020.81. Due to a non-RFC-compliant check of the available authentication methods in the client-side SSH code, it is possible for an SSH server to change the login process in its favor. This attack can bypass additional security measures such as FIDO2 tokens or SSH-Askpass. Thus, it allows an attacker to abuse a forwarded agent for logging on to another server unnoticed.

The weakness was disclosed 10/13/2022. The advisory is shared for download at github.com. This vulnerability is traded as CVE-2021-36369 since 07/09/2021. There are neither technical details nor an exploit publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 216761 (Ubuntu 18.04 LTS / 20.04 LTS / 22.04 LTS : Dropbear vulnerabilities (USN-7292-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2022.82 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be patching the affected component.

The vulnerability is also documented in the vulnerability database at Tenable (216761). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

SSH Server Software

Name

Dropbear

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.9
VulDB Meta Temp Score: 6.7

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

NVD Base Score: 7.5
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: 🔍

Exploitinginfo

Class: Improper authentication
CWE: CWE-287
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: 216761
Nessus Name: Ubuntu 18.04 LTS / 20.04 LTS / 22.04 LTS : Dropbear vulnerabilities (USN-7292-1)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔍

Upgrade: Dropbear 2022.82
Patch: github.com

Timelineinfo

07/09/2021 🔍
10/13/2022 +461 days 🔍
10/13/2022 +0 days 🔍
05/16/2025 +946 days 🔍

Sourcesinfo

Advisory: github.com
Status: Confirmed

CVE: CVE-2021-36369 (🔍)
GCVE (CVE): GCVE-0-2021-36369
GCVE (VulDB): GCVE-100-210732

Entryinfo

Created: 10/13/2022 12:11
Updated: 05/16/2025 03:51
Changes: 10/13/2022 12:11 (42), 11/07/2022 11:12 (11), 02/26/2025 02:11 (16), 05/16/2025 03:51 (1)
Complete: 🔍
Cache ID: 216::103