CVE-2020-3992: VMware ESXi OpenSLP Use-After-Free Vulnerability

100

Patch now

CRITICAL 9.8EXPLOITEDREMOTEUPGRADEMITIGATE

CVE-2020-3992 is a critical-severity flaw (CVSS 9.8) affecting cloud foundation, esxi, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

OpenSLP as used in VMware ESXi (7.0 before ESXi_7.0.1-0.0.16850804, 6.7 before ESXi670-202010401-SG, 6.5 before ESXi650-202010401-SG) has a use-after-free issue. A malicious actor residing in the management network who has access to port 427 on an ESXi machine may be able to trigger a use-after-free in the OpenSLP service resulting in remote code execution.

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
Exploited in the wild (CISA KEV)
Used in ransomware campaigns
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	83.0% (top 1%)
CISA exploited list	Yes, fix due 2022-05-03, used in ransomware
Weakness	CWE-416
Published	2020-10-20
Last modified	2026-08-12

Publisher (CNA): VMware · Vendor: vmware

Last updated 2026-08-12 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-10-20 17:15 UTCPublished CVE record published
2021-11-03Exploited Added to the CISA Known Exploited Vulnerabilities list
2022-05-03Deadline CISA due date for US federal agencies to patch
2026-08-12 05:17 UTCUpdated Record last modified

vmware cloud foundation UPGRADE

Affected: >= 3.0 and < 3.10.1.2 · >= 4.0 and < 4.1.0.1

Fixed in: 3.10.1.2, 4.1.0.1

Safe to downgrade to: a release before 3.0

1. Check installed version

apt-cache policy cloud-foundation || rpm -q cloud-foundation || cloud-foundation --version

2. UPGRADE to 3.10.1.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cloud-foundation

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cloud-foundation

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.0 (Debian / Ubuntu)

apt-cache madison cloud-foundation sudo apt install cloud-foundation=<VERSION_BEFORE_3.0> sudo apt-mark hold cloud-foundation

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list cloud-foundation sudo dnf downgrade cloud-foundation-<VERSION_BEFORE_3.0> sudo dnf versionlock add cloud-foundation

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

vmware esxi MITIGATE

Affected: 6.5 · 6.5 2 · 6.5 650-201701001 · 6.5 650-201703001 · 6.5 650-201703002 · 6.5 650-201704001 · 6.5 650-201707101 · 6.5 650-201707102

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.5

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · feh · FIXED · 3.13.1-1.fc46 · FEDORA-2026-3c76a13a4f · source

sudo dnf upgrade --advisory=FEDORA-2026-3c76a13a4f

Fedora ELN · setroubleshoot · FIXED · 3.3.37-7.eln159 · FEDORA-2026-f81b122fe1 · source

sudo dnf upgrade --advisory=FEDORA-2026-f81b122fe1

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: dgh05t/VMware_ESXI_OpenSLP_PoCs (68 stars)
GitHub PoC: HynekPetrak/CVE-2019-5544_CVE-2020-3992 (50 stars)

Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-3992?

cloud foundation: upgrade to 3.10.1.2, 4.1.0.1; esxi: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-3992 being exploited?

Yes. CVE-2020-3992 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2020-3992 affect?

CVE-2020-3992 affects cloud foundation, esxi. Severity is critical (CVSS 9.8). OpenSLP as used in VMware ESXi (7.0 before ESXi_7.0.1-0.0.16850804, 6.7 before ESXi670-202010401-SG, 6.5 before ESXi650-202010401-SG) has a use-after-free issue. A malicious actor residing in the management network who has access to port 42

How urgent is CVE-2020-3992?

Priority 100/100. Critical severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Used in ransomware campaigns; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

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References

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