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HighPublic exploit

VMware ESXi OpenSLP Heap Overflow RCE

IdentifiersCVE-2021-21974CWE-122

CVE-2021-21974 is a heap-overflow vulnerability in the OpenSLP service as used by VMware ESXi. It affects ESXi 7.0 before ESXi70U1c-17325551, ESXi 6.7 before ESXi670-202102401-SG, and ESXi 6.5 before ESXi650-202102101-SG. According to the provided content, a malicious actor on the same network segment as the ESXi host who can reach port 427 can trigger the heap-overflow condition in OpenSLP, potentially leading to remote code execution on the ESXi hypervisor.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can result in remote code execution on the affected ESXi host. The provided content also states that this vulnerability has been actively exploited in the wild to gain initial access to ESXi servers, including in ransomware campaigns. Post-exploitation activity described in the content includes attempts to stop virtual machines by killing the VMX process and then encrypting VM files. Because exploitation may be used only as the initial access vector, patching alone may not remove malicious code already deployed on the host.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, disable the SLP/OpenSLP service on unpatched ESXi hosts and restrict or block access to port 427 from untrusted systems, especially systems on the same network segment. Re-enable SLP only after updating to a non-vulnerable version. The content notes that disabling SLP may prevent CIM clients from locating CIM servers using SLP.

Remediation

Patch, then assume compromise.

Apply VMware updates to fixed versions or later: ESXi 7.0 to ESXi70U1c-17325551, ESXi 6.7 to ESXi670-202102401-SG, and ESXi 6.5 to ESXi650-202102101-SG. For VMware Cloud Foundation deployments using affected ESXi versions, update to Cloud Foundation 4.2 or later; the content also notes that Cloud Foundation 3.x requires installation of a fix for CVE-2021-21974. Because the vulnerability has been exploited in the wild, perform a full system analysis on previously exposed vulnerable hosts to identify any persistence or payloads dropped before patching.
PUBLIC EXPLOITS

Exploits

2 valid exploits after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).

VALID 2 / 3 TOTALView more in app
CVE-2021-21974MaturityPoCVerified exploit

This repository provides a proof-of-concept (PoC) exploit for CVE-2021-21974, a remote code execution vulnerability in the OpenSLP service of VMware ESXi (7.x and earlier). The main exploit script, '2021-21974-POC.py', is a Python 3 program that connects to the target ESXi host on TCP port 427 (the default OpenSLP port) and sends crafted SLP packets to trigger the vulnerability. Upon successful exploitation, it executes a shell command on the target that creates a named pipe and attempts to establish a reverse shell connection back to the attacker's machine at 192.168.0.194:80 using netcat. The repository also includes a README.md with detailed usage instructions, requirements, and mitigation advice, and a requirements.txt listing Python dependencies. The exploit is intended for educational and research purposes only and is not weaponized; the payload IP address must be changed by the user to receive the reverse shell. The attack vector is network-based, requiring only network access to the vulnerable ESXi host.

mercylessghostDisclosed Jan 10, 2025pythonnetwork
CVE-2021-21974MaturityPoCVerified exploit

This repository contains a proof-of-concept (PoC) exploit for CVE-2021-21974, a remote code execution vulnerability in VMware ESXi 6.7.0 (builds 14320388 and 16316930). The main file, '2021-21974-POC.py', is a Python script that targets the Service Location Protocol (SLP) service on port 427 of a vulnerable ESXi host. The exploit crafts and sends a series of SLP protocol messages to trigger the vulnerability, ultimately allowing the attacker to execute arbitrary shell commands on the target system. By default, the payload establishes a reverse shell from the ESXi host to the attacker's machine at 192.168.0.194:80 using a named pipe at /tmp/backpipe. The script is operational and requires the attacker to specify the target's IP address as a command-line argument. The repository also includes a brief README.md describing the exploit's purpose. No detection scripts or framework integration are present; the code is a standalone exploit PoC.

Shadow0psDisclosed May 25, 2021pythonnetwork
EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
BroadcomCloud Foundationapplication
BroadcomEsxioperating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

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Exposure mapping

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Threat actor evidence3

Every observed campaign linking this CVE to a named adversary.

Associated malware1

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Detection signatures

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Vendor-by-vendor mapping

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Social activity

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