On July 29, 2026, Broadcom released VMware Security Advisory VMSA-2026-0006 addressing five vulnerabilities across VMware ESX, vCenter, Workstation, and Fusion. Three of these flaws carry Critical ratings with CVSS scores of 9.8, 9.8, and 9.3, including a virtual machine escape vulnerability. If you operate VMware infrastructure, this advisory demands immediate attention.
Vulnerability Details
VMSA-2026-0006 covers five distinct CVEs with severity ranging from Critical to Low:
| CVE | Component | CVSS v3.1 | Severity | Attack Vector |
|---|---|---|---|---|
| CVE-2026-59309 | vCenter (VMware Directory Service) | 9.8 | Critical | Network, unauthenticated |
| CVE-2026-59310 | vCenter (Syslog server) | 9.8 | Critical | Network, unauthenticated |
| CVE-2026-47876 | ESX (VMXNET3 virtual network adapter) | 9.3 | Critical | Local, requires VM admin |
| CVE-2026-41703 | ESX, Workstation, Fusion | 7.6 | Important | Network, requires VM deploy privs |
| CVE-2026-41709 | ESX | 2.7 | Low | Local, requires admin |
CVE-2026-59309: vCenter Authentication Bypass
An authentication bypass in the VMware Directory Service allows a malicious actor with network access to vCenter to bypass authentication entirely and gain unauthorized system access. The CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) confirms this is remotely exploitable without credentials or user interaction. Broadcom credits Phil Brass and Matt South of Atredis Partners for reporting this issue.
CVE-2026-59310: vCenter Directory Traversal to RCE
A directory traversal vulnerability in the vCenter syslog server permits an unauthenticated attacker with network access to execute arbitrary code. This shares the same maximum CVSS 9.8 score and attack vector as CVE-2026-59309. The same researchers from Atredis Partners discovered this flaw.
CVE-2026-47876: VMXNET3 VM Escape (CVSS 9.3)
This is the virtual machine escape vulnerability. An attacker who holds local administrative privileges inside a virtual machine using the VMXNET3 paravirtualized network adapter can execute code on the underlying ESX host. The CVSS vector (AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H) shows a scope change (S:C) — the vulnerability crosses the VM-to-host boundary. Non-VMXNET3 adapters (e.g., e1000) are not affected. Nguyen Hoang Thach of STARLabs SG reported this via the Zero Day Initiative's Pwn2Own program.
CVE-2026-41703: Out-of-Bounds Read (CVSS 7.6)
An out-of-bounds read in ESX that a malicious actor with VM deployment privileges could trigger, potentially causing information disclosure or a denial-of-service condition on the host process. On Workstation and Fusion, the impact is limited to information disclosure. Maxim Suhanov (@errno_fail) reported this issue.
CVE-2026-41709: Insufficient Logging (CVSS 2.7)
An insufficient logging vulnerability in ESX that a malicious administrator can exploit to perform certain operations without them being logged. This is a defense-evasion issue rather than a direct exploitation vector.
Impact Assessment
The two vCenter vulnerabilities (CVE-2026-59309 and CVE-2026-59310) are the most immediately dangerous. Both are remotely exploitable without authentication, meaning any attacker who can reach your vCenter management interface on the network can potentially take full control of the vCenter server. From there, they could manage all connected ESX hosts, access virtual machines, and pivot across the virtualization layer.
The VM escape (CVE-2026-47876) requires an attacker to first compromise a virtual machine and gain local administrative privileges, then leverage the VMXNET3 driver to break out to the hypervisor. While this requires more preconditions, VM escapes are among the most severe virtualization vulnerabilities because they violate the fundamental isolation guarantee.
The out-of-bounds read (CVE-2026-41703) primarily threatens availability through DoS, with some information disclosure risk. The logging issue (CVE-2026-41709) is a low-severity defense evasion concern.
Broadcom has found no evidence of in-the-wild exploitation for any of these issues as of the advisory date.
Affected Systems
You are affected if you run any version of the following products prior to the fixed versions listed in the advisory:
- VMware ESX (standalone and within VCF/vSphere Foundation)
- VMware vCenter (standalone and within VCF/vSphere Foundation/Telco Cloud)
- VMware Workstation (versions prior to 26H1)
- VMware Fusion (versions prior to 26H1)
- VMware Cloud Foundation (all versions prior to fixed releases)
- VMware vSphere Foundation (all versions prior to fixed releases)
- VMware Telco Cloud Platform and Telco Cloud Infrastructure
Note: VMware Cloud Foundation 9.0 and vSphere Foundation 9.0 renamed the hypervisor from ESXi to ESX. The terms are used interchangeably in current documentation, though patch identifiers retain the ESXi prefix.
Mitigation & Patching
No workarounds exist for any of these vulnerabilities. The only remediation is applying the fixed versions. Patches are cumulative — installing the latest listed version includes all prior fixes.
vCenter Patches (CVE-2026-59309, CVE-2026-59310)
| Product Line | Version | Fixed Version |
|---|---|---|
| VCF / vSphere Foundation | 9.1.x.x | 9.1.0.0300 |
| VCF / vSphere Foundation | 9.0.x.x | 9.0.2.0100 |
| vCenter (standalone) | 8.0 | 8.0 U3k |
| VCF | 5.x | Async patch to 8.0 U3k (see KB 88287) |
| Telco Cloud Platform | 3.0, 4.x, 5.0.x, 5.1.x | KB 449886 |
| Telco Cloud Infrastructure | 3.0 | KB 449886 |
ESX Patches (CVE-2026-47876, CVE-2026-41703, CVE-2026-41709)
| Product Line | Version | Fixed Version |
|---|---|---|
| VCF / vSphere Foundation | 9.1.x.x | ESXi-9.1.0.0200-25557999 |
| VCF / vSphere Foundation | 9.0.x.x | ESXi-9.0.2.0100-25595025 |
| ESX (standalone) | 8.0 | ESXi80U3k-25595708 |
| VCF | 5.x | Async Patching Guide KB 88287 |
| Telco Cloud Platform | 5.0.x, 5.1.x | KB 449886 |
Workstation & Fusion (CVE-2026-41703)
- Workstation: Update to 26H1
- Fusion: Update to 26H1
On Workstation and Fusion, CVE-2026-41703 is rated Low (CVSS 2.7) with impact limited to information disclosure.
Critical Patching Notes
- Patches are cumulative — The fixed versions listed include all previously released security fixes.
- No workarounds — Network segmentation, firewall rules, or configuration changes cannot mitigate these vulnerabilities.
- Emergency change classification — Broadcom categorizes these updates as emergency changes requiring immediate action per ITIL methodologies.
- Update both vCenter and ESX — The vulnerabilities span both components; patching only one leaves the other exposed.
- VMware Tools not required — CVE-2026-47876 is on the ESX side; updating ESX resolves it. VMware Tools updates are recommended for routine maintenance but not required for this advisory.
- Async patching for VCF 5.x — Follow KB 88287 for the asynchronous patching path.
Detection
Since Broadcom reports no known in-the-wild exploitation, detection focuses on identifying unpatched systems and anomalous activity:
Inventory & Compliance
- Run the Broadcom interoperability matrix to verify vCenter/ESX version compatibility
- Check each vCenter and ESX host against the fixed version tables above
- Use
esxcli software vib liston ESX hosts to verify installed patches - In vCenter, navigate to Lifecycle Manager > Baselines to check compliance
Anomalous Activity Monitoring
- vCenter authentication logs: Watch for unexpected successful logins from unknown sources (CVE-2026-59309)
- Syslog anomalies: Unusual syslog traffic or directory traversal patterns targeting vCenter (CVE-2026-59310)
- VM-to-host breakout attempts: Monitor ESX host logs for unexpected process execution originating from VM contexts, especially involving VMXNET3 interfaces (CVE-2026-47876)
- Privilege escalation: Unexpected admin privilege gains inside VMs followed by host-level activity
Recommended Queries (Splunk/ELK/Suricata)
Frequently Asked Questions
Are these vulnerabilities being exploited in the wild?
Broadcom has no information suggesting active exploitation as of July 29, 2026. However, the absence of evidence is not evidence of absence — the two unauthenticated vCenter RCEs are high-value targets.
Do I need to update both vCenter and ESX?
Yes. CVE-2026-59309 and CVE-2026-59310 affect vCenter. CVE-2026-47876, CVE-2026-41703, and CVE-2026-41709 affect ESX. Patching only one component leaves the other vulnerable.
Is CVE-2026-47876 a true VM escape?
Yes. Broadcom confirms: "An attacker who already holds local administrative privileges inside a virtual machine that uses the VMXNET3 virtual network adapter may execute code on the ESX host." This crosses the VM-to-host isolation boundary (CVSS scope changed).
Can I mitigate CVE-2026-47876 by switching to e1000 network adapters?
Technically, VMs using non-VMXNET3 adapters (like e1000) are not affected by this specific CVE. However, Broadcom advises against this as a strategy — non-paravirtualized adapters have had their own driver vulnerabilities and you lose the 40% I/O performance improvement from paravirtualized drivers. Update ESX instead.
Do I need to update VMware Tools or virtual hardware versions?
No. CVE-2026-47876 resides in the ESX host's VMXNET3 backend; updating ESX resolves it. VMware Tools updates are recommended for routine maintenance but not required for VMSA-2026-0006. Virtual hardware version upgrades are not required.
What about VMware Cloud Foundation 5.x?
VCF 5.x requires async patching to 8.0 U3k. Follow the Asynchronous Patching Guide (KB 88287) for the correct procedure.
Are NSX, VCF Operations, or VCF Automation affected?
No. The VMware FAQ confirms NSX, VCF Operations, and VCF Automation are not affected by VMSA-2026-0006.
How urgent is this?
Broadcom classifies these as emergency changes. The two unauthenticated vCenter RCEs (CVSS 9.8) should be patched immediately. The VM escape (CVSS 9.3) is critical for any multi-tenant or untrusted VM environment. Schedule emergency maintenance windows.
Key Takeaways
- Three Critical CVEs — Two unauthenticated vCenter RCEs (9.8) and one VM escape (9.3) make this a high-priority advisory.
- No workarounds exist — Patching is the only remediation path.
- Patch both vCenter and ESX — The vulnerabilities span the management and compute layers.
- Patches are cumulative — Latest fixed versions include all prior security fixes.
- No known exploitation yet — But the attack surface (internet-exposed vCenter, multi-tenant VMs) warrants rapid action.
- VCF 5.x requires async patching — Follow KB 88287 specifically for that branch.
- Subscribe to VMSA mailing list — Proactive notifications from
go-vmware.broadcom.com/vmsa_email_alertprevent future delays.
Sources:
- Broadcom VMSA-2026-0006 Advisory
- VMware VMSA-2026-0006 Questions & Answers
- The Hacker News Coverage
- VMware Security Response Policy
Automated Transmission
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