Security readout for executives and security teams
Plain-English summary
A flaw in VMware ESXi’s OpenSLP service can let an unauthenticated attacker who can reach port 427 from the management network take control of a host. Compromise could expose workloads, disrupt operations, and undermine the confidentiality and integrity of systems running on that host.
Executive priority
Treat as an immediate remediation priority because the flaw enables unauthenticated remote code execution on virtualization hosts and appears in CISA’s KEV catalog. Prioritize reachable legacy hosts, restrict management-network access during remediation, and verify every host rather than relying on planned patch status.
Technical view
CVE-2020-3992 is a use-after-free vulnerability in OpenSLP on affected VMware ESXi releases. Network access to TCP/UDP port 427 from the management network may permit remote code execution without privileges or user interaction. The supplied CVSS 3.1 score is 9.8, reflecting high confidentiality, integrity, and availability impact.
Likely exposure
Exposure exists where affected ESXi 6.5, 6.7, or 7.0 builds run OpenSLP and port 427 is reachable by a malicious or compromised management-network system. Internet exposure is not required. The supplied evidence does not identify whether any specific environment is vulnerable.
Exploitation context
CISA lists CVE-2020-3992 in its Known Exploited Vulnerabilities catalog, supporting active exploitation in the wild. The vulnerability requires network access to ESXi port 427, making management-network segmentation and access control important, but not substitutes for applying the corrected VMware release.
Researcher notes
The issue is classified as CWE-416, use-after-free. The supplied evidence establishes affected release thresholds, remote code execution potential, port 427 reachability, and KEV status. It does not provide environment-specific compromise indicators, observed attacker behavior, or evidence that access controls alone eliminate the vulnerability.
Mitigation direction
- Upgrade ESXi 7.0 to build ESXi_7.0.1-0.0.16850804 or later.
- Upgrade ESXi 6.7 to ESXi670-202010401-SG or later.
- Upgrade ESXi 6.5 to ESXi650-202010401-SG or later.
- Restrict port 427 access to explicitly authorized management systems.
- Review VMware advisory VMSA-2020-0023 for applicable vendor guidance.
Validation and detection
- Inventory all ESXi hosts and record their exact versions and build numbers.
- Compare each host against the affected version thresholds in the CVE record.
- Identify every network path capable of reaching ESXi port 427.
- Confirm updated hosts report the intended corrected build after maintenance.
- Review host and network telemetry for suspicious port 427 activity.
Public sources used
The source record changed after analysis: Material source record changed after analysis.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-416: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2020-3992 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- Added to KEVCISA-ADP
CISA Known Exploited Vulnerabilities metadata lists this CVE as known exploited.
- ADP timelineCISA-ADP
CVE-2020-3992 added to CISA KEV
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2021-11-03T00:00:00.000Z: CVE-2020-3992 added to CISA KEV
Source materials
- CVE List V5 sourceCVE List V5
- https://www.vmware.com/security/advisories/VMSA-2020-0023.htmlCVE reference, vmware · x_refsource_MISC
- https://www.zerodayinitiative.com/advisories/ZDI-20-1377/CVE reference, vmware · x_refsource_MISC
- https://www.zerodayinitiative.com/advisories/ZDI-20-1385/CVE reference, vmware · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-3992CVE reference, CISA-ADP · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.