Security readout for executives and security teams
Plain-English summary
This is a critical remote code execution flaw in OpenSLP on VMware ESXi. An attacker already positioned on the management network and able to reach port 427 could run code on the hypervisor. Because ESXi hosts underpin many workloads, compromise could affect many systems. CISA KEV indicates known exploitation.
Executive priority
Treat this as urgent for any affected ESXi estate. The vulnerability enables remote code execution on hypervisors, carries critical severity, and is listed by CISA as known exploited. Remediation should be prioritized alongside validation of management network segmentation.
Technical view
CVE-2020-3992 is a CWE-416 use-after-free in OpenSLP as used by VMware ESXi. The published CVSS 3.1 score is 9.8: network exploitable, low complexity, no privileges, and no user interaction. Affected ESXi versions are 7.0, 6.7, and 6.5 before the listed VMware fixed builds.
Likely exposure
Exposure is likely where VMware ESXi 7.0, 6.7, or 6.5 remains below VMware’s fixed builds and port 427 is reachable from the management network. Evidence provided does not establish exposure for other VMware products or non-VMware OpenSLP deployments.
Exploitation context
CISA KEV listing supports known exploitation. The source description limits the attack path to a malicious actor on the management network with access to port 427 on an ESXi host. No source in the bundle provides exploit mechanics, observed campaign details, or ransomware linkage.
Researcher notes
The provided evidence identifies OpenSLP use-after-free behavior in ESXi and remote code execution impact. It does not include proof-of-concept details, exploit telemetry, or non-ESXi affected products. Keep scope limited to VMware ESXi versions and builds named in the CVE and VMware advisory.
Mitigation direction
- Upgrade affected ESXi hosts to VMware’s fixed releases or later.
- Review VMware advisory VMSA-2020-0023 for current vendor remediation guidance.
- Restrict access to ESXi management networks and port 427 to required administrators only.
- Prioritize externally connected or broadly reachable management networks first.
- Track CISA KEV deadlines if operating under applicable federal requirements.
Validation and detection
- Inventory ESXi hosts and record exact build numbers.
- Compare builds against VMware’s fixed versions for 7.0, 6.7, and 6.5.
- Confirm whether port 427 is reachable from management network segments.
- Review network controls limiting access to ESXi management interfaces.
- Check vulnerability management results for CVE-2020-3992 coverage.
Public sources used
Michael Williams reviewed this cited source version on .
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
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:H3.95.9Primary CVE scoreVulnerability 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
Source materials
- CVE List V5 sourceCVE List V5
- https://www.vmware.com/security/advisories/VMSA-2020-0023.htmlCVE reference · x_refsource_MISC
- https://www.zerodayinitiative.com/advisories/ZDI-20-1377/CVE reference · x_refsource_MISC
- https://www.zerodayinitiative.com/advisories/ZDI-20-1385/CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-3992CVE reference · 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.