CVE-2021-21989: VMware Workstation (16.x prior to 16.1.2) and Horizon Client for Windows (5.x prior to 5.5.2) contain out-of-b

Routine

MEDIUM 6.5UPGRADEUPGRADE

CVE-2021-21989 is a medium-severity flaw (CVSS 6.5) affecting workstation, horizon client. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

VMware Workstation (16.x prior to 16.1.2) and Horizon Client for Windows (5.x prior to 5.5.2) contain out-of-bounds read vulnerability in the Cortado ThinPrint component (TTC Parser). A malicious actor with access to a virtual machine or remote desktop may be able to exploit these issues leading to information disclosure from the TPView process running on the system where Workstation or Horizon Client for Windows is installed.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.5% (top 61%)
CISA exploited list	No
Weakness	CWE-125
Published	2021-05-24
Last modified	2026-06-17

Publisher (CNA): VMware · Vendor: vmware

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-05-24 12:15 UTCPublished CVE record published
2026-06-17 03:36 UTCUpdated Record last modified

vmware workstation UPGRADE

Affected: >= 16.0.0 and < 16.1.2

Fixed in: 16.1.2

Safe to downgrade to: a release before 16.0.0

1. Check installed version

apt-cache policy workstation || rpm -q workstation || workstation --version

2. UPGRADE to 16.1.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade workstation

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade workstation

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 16.0.0 (Debian / Ubuntu)

apt-cache madison workstation sudo apt install workstation=<VERSION_BEFORE_16.0.0> sudo apt-mark hold workstation

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

dnf --showduplicates list workstation sudo dnf downgrade workstation-<VERSION_BEFORE_16.0.0> sudo dnf versionlock add workstation

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 horizon client UPGRADE

Affected: >= 5.0.0 and < 5.5.2

Fixed in: 5.5.2

Safe to downgrade to: a release before 5.0.0

1. Check installed version

apt-cache policy horizon-client || rpm -q horizon-client || horizon-client --version

2. UPGRADE to 5.5.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade horizon-client

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade horizon-client

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 5.0.0 (Debian / Ubuntu)

apt-cache madison horizon-client sudo apt install horizon-client=<VERSION_BEFORE_5.0.0> sudo apt-mark hold horizon-client

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

dnf --showduplicates list horizon-client sudo dnf downgrade horizon-client-<VERSION_BEFORE_5.0.0> sudo dnf versionlock add horizon-client

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.

Verify at the official source NVD · CVE Program · 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-2021-21989?

workstation: upgrade to 16.1.2; horizon client: upgrade to 5.5.2. Exact commands for each OS are on this page.

Is CVE-2021-21989 being exploited?

CVE-2021-21989 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-21989 affect?

CVE-2021-21989 affects workstation, horizon client. Severity is medium (CVSS 6.5). VMware Workstation (16.x prior to 16.1.2) and Horizon Client for Windows (5.x prior to 5.5.2) contain out-of-bounds read vulnerability in the Cortado ThinPrint component (TTC Parser). A malicious actor with access to a virtual machine or re

How urgent is CVE-2021-21989?

Priority 33/100. No elevated risk signals yet.

Software pages

Windows vulnerabilities · VMware vulnerabilities · WinRM and RDP vulnerabilities

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References

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