CVE-2021-43399
CVE-2021-43399 is a high-severity vulnerability in Yubico Yubihsm 2 Software Development Kit with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.
Key facts
- Severity: High (CVSS 3.x base score 7.5)
- CVSS v2: 7.8
- EPSS exploit prediction: 1% (69th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-787
- Affected product: Yubico Yubihsm 2 Software Development Kit
- Published:
- Last modified:
Description
The Yubico YubiHSM YubiHSM2 library 2021.08, included in the yubihsm-shell project, does not properly validate the length of some operations including SSH signing requests, and some data operations received from a YubiHSM 2 device.
Frequently asked questions
- What is CVE-2021-43399?
- The Yubico YubiHSM YubiHSM2 library 2021.08, included in the yubihsm-shell project, does not properly validate the length of some operations including SSH signing requests, and some data operations received from a YubiHSM 2 device.
- How severe is CVE-2021-43399?
- CVE-2021-43399 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
- Is CVE-2021-43399 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2021-43399?
- CVE-2021-43399 affects Yubico Yubihsm 2 Software Development Kit. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2021-43399?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- When was CVE-2021-43399 published?
- CVE-2021-43399 was published on 2021-12-08 and last updated on 2026-06-17.
References
- https://blog.inhq.net/posts/yubico-yubihsm-shell-vuln3/
- https://www.yubico.com/support/security-advisories/ysa-2021-04/
Affected products (1)
- cpe:2.3:a:yubico:yubihsm_2_software_development_kit:*:*:*:*:*:*:*:*
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