What is the CVSS score of CVE-2021-21974?

CVE-2021-21974 has a CVSS 3.1 base score of 8.8 (High). CVSS vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 55.0%.

Which versions of VMware are affected by CVE-2021-21974?

CVE-2021-21974 presents significant security risk, a out-of-bounds write vulnerability rated CVSS 8.8.

Is there a public PoC exploit available for CVE-2021-21974?

Yes, a public proof-of-concept exploit is available for CVE-2021-21974. Prioritise patching immediately. EPSS: 55.0%.

How to fix or mitigate CVE-2021-21974?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. If patching is delayed, consider network segmentation to limit exposure.

VMware CVE-2021-21974

HIGH

Out-of-bounds Write (CWE-787)

2021-02-24 security@vmware.com

Buffer Overflow VMware RCE Memory Corruption

8.8

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

8.8 HIGH

AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Adjacent

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 26, 2026 - 11:19 vuln.today

PoC Detected

Nov 21, 2024 - 05:49 vuln.today

Public exploit code

CVE Published

Feb 24, 2021 - 17:15 nvd

HIGH 8.8

DescriptionCVE.org

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.

AnalysisAI

VMware ESXi versions 7.0 before U1c, 6.7 before specific patches, and 6.5 before specific patches contain a heap overflow in the OpenSLP service accessible on port 427. An attacker on the same network segment can trigger remote code execution on the ESXi hypervisor, compromising all virtual machines hosted on the server.

Technical ContextAI

The OpenSLP (Service Location Protocol) service on ESXi listens on UDP/TCP port 427 and is accessible from the management network. A heap overflow in the SLP message parsing allows an attacker on the same network segment to execute arbitrary code in the context of the SLP daemon, which runs with high privileges on the ESXi host.

RemediationAI

Apply VMware security patches immediately. Disable the OpenSLP service if not required (esxcli network firewall ruleset set -e false -r CIMSLP). Restrict port 427 access via ESXi firewall rules. Segment ESXi management networks from general user networks. Implement offline VM backups.