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CVE-2021-31800 is a path traversal vulnerability in smbserver.py in Impacket through version 0.9.22. The vulnerability allows an attacker connected to a running smbserver instance to list and write to arbitrary files on the server by exploiting directory traversal sequences (../). This can be leveraged to overwrite sensitive files such as /etc/shadow or SSH authorized_keys, potentially leading to privilege escalation or arbitrary code execution.
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This repository provides a proof-of-concept exploit for CVE-2021-31800, a critical path traversal vulnerability in Fortra's Impacket smbserver.py. The exploit allows an authenticated attacker to read and write arbitrary files on the SMB server by abusing directory traversal (e.g., using '../' in file paths). The repository is structured with two main environments: 'exploit_env' (containing a patched smbclient.py for exploitation) and 'vulnerable_env' (a Dockerized vulnerable SMB server). The exploit is demonstrated by connecting to the SMB server and issuing commands to traverse directories and access files outside the shared folder. The main exploit logic resides in 'exploit_env/patched/smbclient.py', which is a modified version of Impacket's smbclient.py, enabling the path traversal attack. The repository includes Dockerfiles and Makefiles to easily set up both the exploit and vulnerable environments for testing. The attack vector is network-based, targeting SMB (port 445). No hardcoded IPs or domains are present, but the exploit expects the SMB server to be accessible on the local network.
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