CVE-2021-43399 : Exploit Details and Defense Strategies

The Yubico YubiHSM YubiHSM2 library 2021.08, included in the yubihsm-shell project, has a vulnerability related to improper validation of operation lengths.

Understanding CVE-2021-43399

This CVE pertains to a security issue in the Yubico YubiHSM YubiHSM2 library that affects SSH signing requests and data operations from YubiHSM 2 devices.

What is CVE-2021-43399?

The Yubico YubiHSM YubiHSM2 library 2021.08 in the yubihsm-shell project fails to adequately validate the length of certain operations, creating a security vulnerability.

The Impact of CVE-2021-43399

Attackers could exploit this vulnerability to manipulate SSH signing requests and data operations received from YubiHSM 2 devices.
This may lead to unauthorized access, data manipulation, or other malicious activities.

Technical Details of CVE-2021-43399

The technical details of this CVE are as follows:

Vulnerability Description

The Yubico YubiHSM YubiHSM2 library 2021.08 does not properly validate the length of certain operations, such as SSH signing requests and data operations.

Affected Systems and Versions

Affected version: Yubico YubiHSM YubiHSM2 library 2021.08

Exploitation Mechanism

Attackers can exploit this vulnerability by sending specially crafted SSH signing requests or data operations to a YubiHSM 2 device.

Mitigation and Prevention

To safeguard against CVE-2021-43399, the following steps are recommended:

Immediate Steps to Take

Update the yubihsm-shell project to a patched version that addresses the vulnerability.
Monitor SSH signing requests and data operations for any unusual or potentially malicious activities.

Long-Term Security Practices

Regularly update all software and firmware components related to YubiHSM 2 devices to prevent vulnerabilities.

Patching and Updates

Stay informed about security advisories from Yubico and promptly apply patches to mitigate any known vulnerabilities.