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CVE-2021-21995

25
FAUCET Score

CVE-2021-21995 is a denial-of-service vulnerability in OpenSLP, affecting VMware ESXi and Cloud Foundation, caused by a heap out-of-bounds read. An unauthenticated attacker with network access to port 427 can trigger this flaw, leading to a denial-of-service condition. With a CVSS score of 7.5 (High), it requires no user interaction and has low attack complexity. While not listed in CISA's KEV catalog, there is significant community discussion and media coverage, including reports linking it to ransomware attacks, despite no public exploit code being readily available.

Impacted Technologies

VendorProductVersion(s)CPE
>= 3.0, < 3.10.2CPE matchmatch criteria
cpe:2.3:a:vmware:cloud_foundation:*:*:*:*:*:*:*:*
>= 4.0, < 4.3CPE matchmatch criteria
cpe:2.3:o:vmware:cloud_foundation:*:*:*:*:*:*:*:*
6.5CPE matchmatch criteria
cpe:2.3:o:vmware:esxi:6.5:-:*:*:*:*:*:*
6.5CPE matchmatch criteria
cpe:2.3:o:vmware:esxi:6.5:650-201701001:*:*:*:*:*:*
6.5CPE matchmatch criteria
cpe:2.3:o:vmware:esxi:6.5:650-201703001:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.96%
Probability of exploitation in next 30 days
EPSS Percentile
57.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0096 is in the 33rd percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

vmwarevendor investigatingvia nvd_reference
View patch

References

vmware.com / security/advisories/VMSA-2021-0014.html
Vendor Advisory