Improper authentication in Dropbear - CVE-2021-36369
Published: August 20, 2023
Vulnerability identifier: #VU79726
CSH Severity: Medium
CVSS v4: 5.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2021-36369
CWE-ID: CWE-287
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to bypass authentication process.
The vulnerability exists due to a non-RFC-compliant check of the available authentication methods in the client-side SSH code. A remote user can bypass additional security measures such as FIDO2 tokens or SSH-Askpass and abuse a forwarded agent for logging on to another server unnoticed.
Affected software
Dropbear
Fedora
Ubuntu
dropbear (Ubuntu package)
dropbear-bin (Ubuntu package)
dropbear
Fedora
Ubuntu
dropbear (Ubuntu package)
dropbear-bin (Ubuntu package)
dropbear
How to mitigate CVE-2021-36369
Install updates from vendor's website.
Dropbear - update to 2022.82
dropbear (Ubuntu package) - addressed in versions Ubuntu Pro, 2020.81-5ubuntu0.1
dropbear-bin (Ubuntu package) - addressed in versions Ubuntu Pro, 2020.81-5ubuntu0.1
dropbear - addressed in versions 2017.75-3.el7, 2019.78-5.el8, 2020.80-7.el9
dropbear (Ubuntu package) - addressed in versions Ubuntu Pro, 2020.81-5ubuntu0.1
dropbear-bin (Ubuntu package) - addressed in versions Ubuntu Pro, 2020.81-5ubuntu0.1
dropbear - addressed in versions 2017.75-3.el7, 2019.78-5.el8, 2020.80-7.el9