Skip to content
Fencer Vulns
high 8.8

CVE-2021-21974 in the critical feed json

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-overfl…

published 2021-02-24 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-9145

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
45.1%
EPSS 45.1% chance of exploitation in 30 days, percentile 98%
public exploits
0
none known

Summary

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.

Patch / fix

  • vmware cloud_foundation 3.10.1.2, 4.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-21974 updated cvss 8.8

OpenSLP: heap-overflow

  • Red Hat Enterprise Linux 6 openslp, openslp-server Red Hat Enterprise Linux 7 openslp, openslp-server Red Hat Enterprise Linux 8 openslp Red Hat Enterprise Linux 9 openslp, openslp-server
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Ransomware

Groups reported to have exploited it in intrusions.

  • ESXiArgs ransomware gang

reported by greynoise.io

Ransomware Vulnerability Matrix by BushidoUK (github.com/BushidoUK/Ransomware-Vulnerability-Matrix), reformatted per CVE. CC BY 4.0

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
5 mo ago

Exploit prediction

45.06% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • packetstormsecurity.com http://packetstormsecurity.com/files/162957/VMware-ESXi-OpenSLP-Heap-Overflow.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 8.8 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 8.8 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 8.8 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 5.8 AV:A/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • n/a VMware ESXi
  • n/a VMware Cloud Foundation

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.