OpenSLP Heap Overwrite in VMware ESXi and Horizon DaaS
Actively exploited in the wild. Patch or mitigate immediately — don't wait for a maintenance window.
An unauthenticated attacker, remotely over the network, with no user interaction, can fully compromise the system — steal data, tamper with it and take it offline.
OpenSLP as used in ESXi and the Horizon DaaS appliances has a heap overwrite issue. VMware has evaluated the severity of this issue to be in the Critical severity range with a maximum CVSSv3 base score of 9.8.
Inferred from the weakness type (CWE) and how the flaw is reached — the techniques an attacker would chain to exploit this. Real-world corroboration appears here as threat intel is folded in.
Corroborated threat activity referencing this CVE — with source and confidence, not inference.
Named threat actors and observed ATT&CK techniques appear here as intel feeds are folded in — the ATT&CK chain above stays inferred until then.
Generated by Wavense from the CVE record — an immediate mitigation and the permanent fix.
Restrict network access to the SLP service (port 427 UDP/TCP) on ESXi hosts and Horizon DaaS appliances, ideally isolating them from untrusted networks. If the SLP service is not critical for operational functionality, consider temporarily disabling it to eliminate the attack surface. Implement robust network intrusion detection systems to monitor for anomalous traffic patterns targeting port 427.
The permanent resolution involves applying the vendor-provided security patches for VMware ESXi and Horizon DaaS. Consult VMware's official security advisories (VMSA-2019-0013) for specific patch versions and upgrade instructions relevant to your environment. Ensure all affected instances are updated to a patched version to remediate the heap overwrite vulnerability.
An attacker can achieve arbitrary code execution with elevated privileges on affected ESXi hosts or Horizon DaaS appliances. This can lead to a complete compromise of the hypervisor or DaaS environment, giving the attacker full control over all hosted virtual machines, sensitive data, and critical network infrastructure. The business consequences include severe data breaches, system downtime, and potential loss of intellectual property.
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A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..