Is CVE-2021-21974 actively exploited?

Yes. CVE-2021-21974 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, which means exploitation in the wild has been confirmed.

Can CVE-2021-21974 be exploited remotely?

The attack vector of CVE-2021-21974 has not been classified yet.

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

CVE-2021-21974 has not received a CVSS score yet.

HOME VULNERABILITIESCVE-2021-21974

UNKNOWNCISA KEVIN THE WILD

CVE-2021-21974

Published: April 11, 2026

EPSS:55.70%probability of exploitation in 30 daysPercentile:98.1th

Official 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.

NVD Source

Technical Analysis

CVE-2021-21974 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

CISA has added CVE-2021-21974 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.