CVE-2023-20892 Overview
CVE-2023-20892 is a heap overflow vulnerability in VMware vCenter Server caused by the use of uninitialized memory in the Distributed Computing Environment / Remote Procedure Call (DCERPC) protocol implementation. An unauthenticated attacker with network access to vCenter Server can trigger the flaw to execute arbitrary code on the underlying host operating system. The issue affects vCenter Server 7.0 and 8.0 release lines and was addressed by VMware in VMware Security Advisory VMSA-2023-0014. The flaw is tracked under CWE-787 Out-of-Bounds Write and carries an EPSS probability of 3.533% (87.8th percentile).
Critical Impact
An unauthenticated network attacker can achieve remote code execution on the vCenter Server host, compromising the management plane of the entire vSphere environment.
Affected Products
- VMware vCenter Server 7.0 (all updates through Update 3l)
- VMware vCenter Server 8.0 (releases through Update 1a)
- VMware Cloud Foundation deployments that bundle the affected vCenter Server versions
Discovery Timeline
- 2023-06-22 - CVE-2023-20892 published to NVD
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2023-20892
Vulnerability Analysis
The vulnerability resides in the DCERPC protocol handler used by vCenter Server. DCERPC is the remote procedure call mechanism inherited from the Open Group Distributed Computing Environment specification. The server allocates heap memory while processing DCERPC requests but does not fully initialize the buffer before use. Attacker-controlled bytes flow into adjacent heap regions, producing a write past the intended bounds.
Because the protocol is exposed on the network and requires no authentication, an attacker only needs reachability to the vCenter management interfaces. Successful exploitation grants code execution in the context of the vCenter Server service, which manages ESXi hosts, virtual machines, and credentials across the cluster.
Root Cause
The root cause is the consumption of uninitialized heap memory inside the DCERPC parsing routines. Buffer length fields supplied in the request are trusted during downstream copy operations, allowing a crafted request to overflow the heap chunk. This pattern is classified as CWE-787 Out-of-Bounds Write and overlaps with uninitialized memory use weaknesses.
Attack Vector
The attack vector is purely network-based. An attacker sends a crafted DCERPC message to an exposed vCenter Server endpoint. No user interaction or prior credentials are required. After the heap is corrupted, the attacker can pivot to arbitrary code execution under the privileges of the vCenter Server process, then move laterally to managed ESXi hosts. Technical analysis is documented in the Talos Intelligence Vulnerability Report TALOS-2023-1801.
Detection Methods for CVE-2023-20892
Indicators of Compromise
- Unexpected child processes spawned by the vCenter Server vmware-vpxd or related DCERPC service accounts.
- Abnormal crashes or restarts of vCenter Server services correlated with inbound DCERPC traffic.
- Outbound network connections from the vCenter appliance to unfamiliar external hosts immediately following inbound RPC sessions.
Detection Strategies
- Inspect network traffic to vCenter Server for malformed DCERPC PDUs with anomalous fragment sizes or unusual interface UUIDs.
- Monitor vCenter Server appliance logs under /var/log/vmware/ for repeated protocol parsing errors, segmentation faults, or service restarts.
- Apply endpoint behavioral analytics on the vCenter host to flag shell, scripting, or reconnaissance binaries spawned by RPC-related processes.
Monitoring Recommendations
- Restrict and log all access to vCenter management ports, alerting on connections from sources outside the administrative network.
- Forward vCenter audit and service logs to a centralized SIEM and correlate them with network flow records.
- Validate inventory of vCenter Server builds against the fixed versions listed in VMSA-2023-0014 on a recurring basis.
How to Mitigate CVE-2023-20892
Immediate Actions Required
- Upgrade vCenter Server 7.0 to build 7.0 U3m and vCenter Server 8.0 to build 8.0 U1b or later, as listed in VMSA-2023-0014.
- Place vCenter Server on an isolated management network reachable only from administrator jump hosts.
- Audit recent DCERPC traffic and vCenter service crashes for signs of attempted exploitation before patching.
Patch Information
VMware released fixed builds for both supported release lines in VMware Security Advisory VMSA-2023-0014. Administrators should consult the advisory for the exact build numbers corresponding to their deployment, including VMware Cloud Foundation customers who must apply the asynchronous patch matrix for vCenter Server.
Workarounds
- No supported workaround removes the vulnerability; patching is the only complete remediation per VMware guidance.
- As a temporary control, restrict network reachability to vCenter Server management interfaces using firewalls and ACLs limited to trusted administrative sources.
- Disable or block exposure of unused DCERPC endpoints at the perimeter where feasible until patches are deployed.
# Example firewall restriction limiting vCenter management access to a trusted admin subnet
iptables -A INPUT -p tcp -s 10.10.50.0/24 -d <vcenter_ip> --dport 443 -j ACCEPT
iptables -A INPUT -p tcp -d <vcenter_ip> --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
