How severe is CVE-2021-21974?

CVE-2021-21974 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-21974 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 45% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21974?

CVE-2021-21974 primarily affects Vmware Cloud Foundation. In total, 232 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-21974?

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-2021-21974 published?

CVE-2021-21974 was published on 2021-02-24 and last updated on 2026-06-17.

CVE-2021-21974

CVE-2021-21974 is a high-severity vulnerability in Vmware Cloud Foundation with a CVSS 3.x base score of 8.8. Its EPSS exploit-prediction score of 45% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-787.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 5.8
EPSS exploit prediction: 45% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Vmware Cloud Foundation
Published: 2021-02-24
Last modified: 2026-06-17

Description

OpenSLP as used in ESXi (7.0 before ESXi70U1c-17325551, 6.7 before ESXi670-202102401-SG, 6.5 before ESXi650-202102101-SG) has a heap-overflow vulnerability. A malicious actor residing within the same network segment as ESXi who has access to port 427 may be able to trigger the heap-overflow issue in OpenSLP service resulting in remote code execution.

Frequently asked questions

What is CVE-2021-21974?: OpenSLP as used in ESXi (7.0 before ESXi70U1c-17325551, 6.7 before ESXi670-202102401-SG, 6.5 before ESXi650-202102101-SG) has a heap-overflow vulnerability. A malicious actor residing within the same network segment as ESXi who has access to port 427 may be able to trigger the heap-overflow issue in OpenSLP service resulting in remote code execution.
How severe is CVE-2021-21974?: CVE-2021-21974 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-21974 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 45% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21974?: CVE-2021-21974 primarily affects Vmware Cloud Foundation. In total, 232 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-21974?: 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-2021-21974 published?: CVE-2021-21974 was published on 2021-02-24 and last updated on 2026-06-17.

References

Affected products (232)

cpe:2.3:a:vmware:cloud_foundation:*:*:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:-:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:2:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201701001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201703001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201703002:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201704001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707101:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707102:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707103:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707201:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707202:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707203:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707204:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707205:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707206:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707207:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707208:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707209:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707210:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707211:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707212:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707213:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707214:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707215:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707216:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707217:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707218:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707219:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707220:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201707221:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201710001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201712001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201803001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201806001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201808001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201810001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201810002:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201811001:*:*:*:*:*:*
cpe:2.3:o:vmware:esxi:6.5:650-201811002:*:*:*:*:*:*

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