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DETECTION OVERVIEW

Windows NFS Exploit Attempt - CVE-2020-17051

Risk Factors

Attackers must have write permission for any NFS share on the targeted system. However, authentication is not required if the NFS share is configured with anonymous write access. If the exploit is successful, the attacker can cause a denial of service (DoS) or gain control of the Windows Server. This exploit is wormable between machines hosting writable NFS shares.

Kill Chain

Exploitation

Risk Score

88

Detection diagram
Next in Exploitation: Windows NFS ONCRPC Exploit Attempt - CVE-2021-26432

Attack Background

Windows NFS v3 is a file server that can be deployed in environments that include Windows and Linux. Windows NFS v3 has a vulnerability in how it validates field size and buffer values for certain NFS requests. An attacker can create an NFS request with manipulated size and buffer values that result in a heap overflow in the NFS driver (nfssvr.sys). The heap overflow can lead to a denial of service (DoS) or remote code execution (RCE).

Mitigation Options

Install relevant patches for affected versions

Disable anonymous write access to NFS shares unless required

Restrict file share access to only authorized IP addresses and hosts

MITRE ATT&CK ID

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