What’s Vulnerable › Vulnerabilities

CVE-2021-28484

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-04-14 · updated 2026-06-17
• Weakness: CWE-835

Description

An issue was discovered in the /api/connector endpoint handler in Yubico yubihsm-connector before 3.0.1 (in YubiHSM SDK before 2021.04). The handler did not validate the length of the request, which can lead to a state where yubihsm-connector becomes stuck in a loop waiting for the YubiHSM to send it data, preventing any further operations until the yubihsm-connector is restarted. An attacker can send 0, 1, or 2 bytes to trigger this.

Affected products

• Fedoraproject Fedora: 34
• Yubico Yubihsm Connector: before 3.0.1 — fixed in 3.0.1

How to fix

Upgrade to a fixed version: Yubico Yubihsm Connector 3.0.1. Check the vendor advisory for mitigations.

References

• https://github.com/Yubico/yubihsm-connector/releases
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B7Q2KGXSPQEEONAWMFZRVH2TXWX3QPCQ/
• https://www.yubico.com/support/security-advisories/ysa-2021-02/
• https://github.com/Yubico/yubihsm-connector/releases
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B7Q2KGXSPQEEONAWMFZRVH2TXWX3QPCQ/
• https://www.yubico.com/support/security-advisories/ysa-2021-02/

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