Broadcom released critical security updates today for VMware ESXi, vCenter, Workstation, and Fusion addressing five vulnerabilities, including a VM escape flaw in the VMXNET3 virtual network adapter that allows a guest with local admin privileges to execute code on the host.

Vulnerability Details

Three vulnerabilities carry a Critical severity rating with CVSS scores up to 9.8:

CVE	Component	CVSSv3	Severity	Attack Vector
CVE-2026-59309	vCenter Directory Service	9.8	Critical	Network (AV:N)
CVE-2026-59310	vCenter Syslog Server	9.8	Critical	Network (AV:N)
CVE-2026-47876	ESXi VMXNET3 Adapter	9.3	Critical	Local (AV:L), Scope Changed
CVE-2026-41703	ESXi/Workstation/Fusion	7.6	Important	Network (AV:N)
CVE-2026-41709	ESXi Logging	2.7	Low	Network (AV:N)

CVE-2026-47876: VMXNET3 VM Escape (CVSS 9.3)

This is the most significant vulnerability for virtualization administrators. An out-of-bounds write in the VMXNET3 virtual network adapter allows a malicious actor with local administrative privileges on a virtual machine to execute arbitrary code on the ESXi host.

• Scope Changed (S:C): The vulnerability crosses the guest-host boundary
• No user interaction required (UI:N)
• No privileges required on the host (PR:N)
• Affected: All ESXi versions 8.0, 9.0.x, 9.1.x with VMXNET3 adapter
• Not affected: Other virtual adapter types (E1000, VMXNET2, etc.)
• Reported by: Nguyen Hoang Thach (@hi_im_d4rkn3ss) of STARLabs SG via Pwn2Own/Zero Day Initiative

This is a classic VM escape -- the "holy grail" of virtualization vulnerabilities -- where compromise of a single guest leads to host compromise and potentially all other VMs on that host.

CVE-2026-59309: vCenter Authentication Bypass (CVSS 9.8)

An authentication bypass in the VMware Directory Service allows unauthenticated attackers with network access to vCenter to gain unauthorized system access. This affects vCenter 8.0, 9.0.x, and 9.1.x across all deployment models (standalone, Cloud Foundation, Telco Cloud).

CVE-2026-59310: vCenter Directory Traversal to RCE (CVSS 9.8)

A directory traversal flaw in the vCenter Syslog server component allows unauthenticated network attackers to execute arbitrary code. Combined with CVE-2026-59309, this creates a devastating attack chain: bypass authentication, then achieve RCE.

Both vCenter flaws were reported by Phil Brass and Matt South of Atredis Partners.

Impact Assessment

Who Is Affected

Any organization running:

• VMware ESXi 8.0 or 9.x
• VMware vCenter 8.0 or 9.x
• VMware Workstation 25H2 (Windows/Linux)
• VMware Fusion 25H2 (macOS)
• VMware Cloud Foundation 5.x, 9.0.x, 9.1.x
• VMware vSphere Foundation
• VMware Telco Cloud Platform/Infrastructure

What Is at Risk

Asset	Risk
ESXi Hosts	Full compromise via VM escape (CVE-2026-47876)
vCenter Server	Complete takeover via auth bypass + RCE chain (CVE-2026-59309/59310)
Guest VMs	Lateral movement from compromised host
Management Network	Pivot point for further intrusion
Workstation/Fusion	Local privilege escalation on developer machines

Attack Scenarios

1. VM Escape: Compromise a single VM -> escalate to host -> access all VMs on that host
2. vCenter Takeover: Network access to vCenter -> auth bypass -> RCE -> control entire vSphere environment
3. Combined Chain: vCenter compromise -> deploy malicious VMs -> VM escape -> host compromise

Affected Systems and Fixed Versions

ESXi (CVE-2026-47876, CVE-2026-41703, CVE-2026-41709)

Product Line	Version	Fixed Build
ESXi 8.0	8.0 U3k	ESXi80U3k-25595708
ESXi 9.0.x	9.0.x	ESXi-9.0.2.0100-25595025
ESXi 9.1.x	9.1.x	ESXi-9.1.0.0200-25557999
Cloud Foundation 5.x	5.x	Async patch (KB88287)
Telco Cloud Platform	5.0.x, 5.1.x	KB449886

vCenter (CVE-2026-59309, CVE-2026-59310)

Product Line	Version	Fixed Version
vCenter 8.0	8.0	8.0 U3k
vCenter 9.0.x	9.0.x	9.0.2.0100
vCenter 9.1.x	9.1.x	9.1.0.0300
Cloud Foundation	5.x	Async patch to 8.0 U3k
Telco Cloud Platform	3.0, 4.x, 5.0.x, 5.1.x	KB449886

Workstation and Fusion (CVE-2026-41703)

Product	Fixed Version
Workstation Pro	26H1
Fusion Pro	26H1

Mitigation and Patching

Immediate Actions

1. Inventory all affected assets -- Identify every ESXi host, vCenter, Workstation, and Fusion instance
2. Prioritize vCenter patching -- CVE-2026-59309/59310 are remotely exploitable without authentication
3. Patch ESXi hosts -- Especially those running VMXNET3 adapters on untrusted guest workloads
4. Update Workstation/Fusion -- Developer machines are often overlooked

Patching Procedure

For vCenter (Appliance):

For ESXi Hosts:

For Cloud Foundation: Follow the Async Patching Guide (KB88287)

Verification Commands

Detection

Network Indicators

• Unexpected connections to vCenter on ports 443, 5480, 389, 636
• Anomalous syslog traffic to vCenter Syslog port (514/1514)
• VMXNET3 driver crash logs in /var/log/vmkernel.log

Host-Based Indicators

YARA Rule for VMXNET3 Exploit Artifacts

Suricata Rule for vCenter Exploitation Attempts

Frequently Asked Questions

Is there any workaround if I cannot patch immediately?

No. Broadcom explicitly states there are no workarounds for any of these five vulnerabilities. The only remediation is applying the patches.

Does this affect VMware Cloud on AWS / Azure VMware Solution / Google Cloud VMware Engine?

Yes, these managed services run on the same underlying ESXi and vCenter versions. However, the cloud providers typically handle patching on their maintenance schedules. Contact your provider for their specific timeline.

My VMs use E1000 or VMXNET2 adapters. Am I safe from the VM escape?

Yes, for CVE-2026-47876 specifically. The vulnerability only affects the VMXNET3 virtual network adapter. However, you should still patch for the other vulnerabilities (CVE-2026-41703, CVE-2026-41709) and the vCenter flaws.

How do I check which virtual network adapters my VMs use?

Are these vulnerabilities being exploited in the wild?

Broadcom states they are not aware of in-the-wild exploitation as of the advisory date (July 29, 2026). However, given the severity and the fact that CVE-2026-47876 was demonstrated at Pwn2Own, weaponized exploits likely exist or will emerge quickly.

What about older ESXi versions (7.0, 6.7)?

ESXi 7.0 reached End of General Support on October 2022. ESXi 6.7 is End of Life. These versions do not receive security patches. Upgrade immediately or isolate these hosts completely.

Key Takeaways

1. Three Critical vulnerabilities affect the core of vSphere: two in vCenter (auth bypass + RCE), one in ESXi (VM escape)
2. No workarounds exist -- patching is mandatory
3. VM escape (CVE-2026-47876) is the highest-impact flaw for multi-tenant environments
4. vCenter flaws (CVE-2026-59309/59310) enable full infrastructure takeover from the network
5. Patches are cumulative -- latest versions include all prior fixes
6. Developer workstations running Workstation/Fusion 25H2 are also vulnerable and often overlooked
7. Inventory and prioritize: vCenter -> ESXi hosts with VMXNET3 -> Workstation/Fusion

Conclusion

Today's VMSA-2026-0006 advisory addresses the most dangerous class of virtualization vulnerabilities: those that break the isolation boundary between guest and host, and those that compromise the central management plane. Organizations running VMware infrastructure should treat this as a maximum-priority patch cycle.

The VMXNET3 VM escape (CVE-2026-47876) is particularly noteworthy -- discovered through the Pwn2Own contest, it demonstrates that even mature hypervisors harbor subtle memory safety bugs in virtual device emulators. The dual vCenter criticals (CVE-2026-59309/59310) form a devastating chain: authentication bypass followed by remote code execution, both requiring zero credentials.

Patch now. Verify after. Monitor continuously.

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Sources:

• Broadcom VMSA-2026-0006 Advisory
• SecurityWeek: Critical VM Escape Vulnerability Patched in VMware ESXi
• VMware Security FAQ for VMSA-2026-0006