CVE-2021-27217: Yubico Yubihsm-Shell

Medium severity, CVSS 4.4. EPSS: 1.6% chance of exploitation in the next 30 days.

An issue was discovered in the _send_secure_msg() function of Yubico yubihsm-shell through 2.0.3. The function does not correctly validate the embedded length field of an authenticated message received from the device. Out-of-bounds reads performed by aes_remove_padding() can crash the running process, depending on the memory layout. This could be used by an attacker to cause a client-side denial of service. The yubihsm-shell project is included in the YubiHSM 2 SDK product.

Affected products

• Yubico Yubihsm-Shell: up to and including 2.0.3

Published 2021-03-04. Last modified 2026-06-17.