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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 3 May 2022. Known ransomware use
Horizon DaasApplication · VMware

CVE-2019-5544

CRITICAL · 9.8 CVSS v3.1 Published 2019-12-06
Fix available
A fix is available. Upgrade to 9.0.0.0 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Ransomware High EPSS Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
OpenSLP as used in ESXi and the Horizon DaaS appliances has a heap overwrite issue. VMware has evaluated the severity of this issue to be in the Critical severity range with a maximum CVSSv3 base score of 9.8.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A heap overwrite vulnerability exists in the OpenSLP implementation used by VMware ESXi and Horizon DaaS appliances. This memory corruption flaw could allow an unauthenticated remote attacker to execute arbitrary code by sending specially crafted SLP packets, potentially achieving full system compromise.

MitigationApply VMware security patches for ESXi and Horizon DaaS as soon as possible; network segmentation of SLP services may serve as a temporary workaround if patching is immediately infeasible.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Horizon DaasApplication
Affected:>= 8.0.0, < 9.0.0.0
EsxiOperating system
Affected:= 6.0= 6.5= 6.7
Enterprise Linux DesktopOperating system
Affected:= 6.0= 7.0
Enterprise Linux For Ibm Z SystemsOperating system
Affected:= 6.0_s390x= 7.0_s390x
Enterprise Linux For Ibm Z Systems EusOperating system
Affected:= 7.7_s390x
Enterprise Linux For Power Big EndianOperating system
Affected:= 6.0_ppc64= 7.0_ppc64
Enterprise Linux For Power Big Endian EusOperating system
Affected:= 7.7_ppc64
Enterprise Linux For Power Little EndianOperating system
Affected:= 7.0_ppc64le

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed product and version
    For VMware ESXi, run 'vmware -v' or check the ESXi host client for version. For Horizon DaaS, check the admin console or run 'vdmadmin -version'. For RHEL, run 'cat /etc/redhat-release'.
    Affected if The product matches VMware ESXi 6.0, 6.5, or 6.7; VMware Horizon Daas 8.x; or RHEL 6.0/7.0 variants listed in affected versions.
  2. Verify OpenSLP service is present
    Check if the OpenSLP daemon is installed: on RHEL run 'rpm -qa | grep -i slp' or 'systemctl list-unit-files | grep slp'. On ESXi, check for '/usr/lib/vmware/openslp' or similar paths.
    Affected if OpenSLP package or service files exist on the system.
  3. Confirm OpenSLP is running or enabled
    On RHEL, run 'systemctl status slpd' or check if port 427 is listening: 'netstat -an | grep 427' or 'ss -tlnp | grep 427'.
    Affected if The SLP service (port 427/TCP or UDP) is listening or the slpd service is active.
  4. Check OpenSLP package version on RHEL
    Run 'rpm -q openslp' to retrieve the installed package version and compare against any available patched versions.
    Affected if OpenSLP is installed and the version is among the affected RHEL releases (6.0 or 7.0 variants).

The system is affected if it runs a listed VMware ESXi, Horizon Daas, or RHEL version AND has the OpenSLP service enabled and listening on port 427.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 9.0.0.0 or later
Fixed in 9.0.0.0
Vendor patch www.vmware.com →
Interim mitigation

Apply VMware security patches for ESXi and Horizon DaaS as soon as possible; network segmentation of SLP services may serve as a temporary workaround if patching is immediately infeasible.

Recommended fix High confidence

VMware ESXi: 6.0 -> 6.0 U3k or later, 6.5 -> 6.5 U3 or later, 6.7 -> 6.7 U3 or later; Horizon DaaS: 8.x -> 9.0.0 or later; RHEL: 6.x -> 6.10 or later, 7.x -> 7.7 or later (with EUS channels)

  1. For VMware ESXi: Apply VMware Security Advisory VMSA-2020-0001 or subsequent security patches addressing CVE-2019-5544
  2. For VMware ESXi: Update to ESXi 6.0 patch ESXi670-202011001 or later, ESXi650-202011001 or later, or ESXi600-202011001 or later
  3. For Red Hat Enterprise Linux: Run 'yum update openslp' or 'yum update openslp-devel' to apply security patches
  4. For Red Hat Enterprise Linux: Apply RHSA-2020:0573 or subsequent Red Hat Security Advisory for openslp
Caveat Upgrading ESXi may require VM downtime and should be tested in non-production environment first; RHEL minor version upgrades via EUS require appropriate subscription

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Horizon Daas Exploited in the wild — priority engagement
  • Consultation8.0 h
  • Implementation12.0 h
  • Testing16.0 h
  • Review / QA4.0 h
40.0 hours of engineering $6,880
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $11,008.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-5544 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data