How severe is CVE-2021-20487?

CVE-2021-20487 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-20487 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20487?

CVE-2021-20487 primarily affects Ibm Power9 System Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20487?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-20487 published?

CVE-2021-20487 was published on 2021-05-26 and last updated on 2026-06-17.

CVE-2021-20487

CVE-2021-20487 is a critical-severity vulnerability in Ibm Power9 System Firmware with a CVSS 3.x base score of 9.1. 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-347.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v2: 6.5
EPSS exploit prediction: 1% (48th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-347
Affected product: Ibm Power9 System Firmware
Published: 2021-05-26
Last modified: 2026-06-17

Description

IBM Power9 Self Boot Engine(SBE) could allow a privileged user to inject malicious code and compromise the integrity of the host firmware bypassing the host firmware signature verification process.

Frequently asked questions

What is CVE-2021-20487?: IBM Power9 Self Boot Engine(SBE) could allow a privileged user to inject malicious code and compromise the integrity of the host firmware bypassing the host firmware signature verification process.
How severe is CVE-2021-20487?: CVE-2021-20487 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-20487 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20487?: CVE-2021-20487 primarily affects Ibm Power9 System Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20487?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-20487 published?: CVE-2021-20487 was published on 2021-05-26 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:o:ibm:power9_system_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:ibm:scale-out_lc_system_firmware:*:*:*:*:*:*:*:*

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