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CVE-2021-21974 is a critical heap-overflow vulnerability that impacts the OpenSLP service in VMware ESXi.
The flaw specifically resides within the service listening on network port 427.
This port handles Service Location Protocol discovery requests across local network segments.
When an unauthenticated malicious actor sends a crafted request packet, memory allocation fails.
The application fails to correctly calculate buffer boundaries when processing data lengths.
This memory management flaw triggers a classic heap-based buffer overflow condition.
Because the OpenSLP service operates with elevated privileges, memory corruption leads directly to system compromise.
An attacker with network access to port 427 can achieve remote code execution.
Successful exploitation allows the adversary to take full control of the underlying hypervisor.
No user interaction or prior authentication is required to trigger this vulnerability.
Enterprise virtual infrastructures hosting multiple virtual machines face catastrophic failure if compromised.
Threat actors can leverage this access to deploy encrypting ransomware across all guests.
VMware released official patches and workarounds to disable the vulnerable service entirely.
Administrators are strongly advised to disable the SLP service if network discovery is unnecessary.
Continuous monitoring of port 427 traffic helps detect abnormal payload sizes and exploitation attempts.
Understanding this mechanism highlights the importance of rigorous input validation in system daemons.
Memory safety issues in legacy network protocols continue to present major attack vectors.
Isolating management interfaces onto secure administrative VLANs remains a critical defense strategy.
Network segmentation limits exposure to potential lateral movement from compromised segments.
Security teams track such exploits closely within repositories like GhostTroops TOP for threat intelligence.
DailyCVE Form:
Platform: VMware ESXi
Version: v6.5, v6.7, v7.0
Vulnerability : OpenSLP Heap Overflow
Severity : Critical Risk
date: Feb 23 2021
Prediction: Patched Long Ago
What Undercode Say:
Scan target for open SLP port 427 nmap -p 427 --script slp-discovery <target-ip> Check ESXi version via local CLI vmware -v Stop and disable the vulnerable OpenSLP service esxcli system slp services stop esxcli system slp services unregister
How Exploit: (Educational Purposes!)
An attacker initiates an unauthenticated connection to port 427 running on the target VMware ESXi host. By transmitting a meticulously crafted malicious Service Location Protocol packet containing oversized header fields, the OpenSLP daemon encounters a heap memory allocation discrepancy. As the service processes the malformed input without adequate bounds checking, data spills over the allocated heap chunk, corrupting adjacent memory structures and hijacking the instruction pointer to execute arbitrary shellcode payloads.
Protection:
To protect systems against CVE-2021-21974, administrators must apply the official security patches provided by VMware. If patching is immediately unfeasible, the vulnerable OpenSLP service should be disabled entirely by stopping the daemon via the ESXi command-line interface and blocking port 427 at the network perimeter firewall layer. Additionally, restricting management network access to trusted administrative hosts mitigates unauthorized exposure.
Impact:
The impact of this vulnerability is severe, resulting in complete compromise of confidentiality, integrity, and availability. Successful remote code execution grants the attacker unauthenticated administrative control over the ESXi hypervisor, enabling them to manipulate, access, or destroy all hosted virtual machines, steal sensitive enterprise data, and deploy ransomware across the entire infrastructure.
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Sources:
Reported By: github.com
Extra Source Hub:
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