The Gravity updater in Pi-hole through 4.4 allows an authenticated adversary to upload arbitrary files. This can be abused for Remote Code Execution by writing to a PHP file in the web directory. (Also, it can be used in conjunction with the sudo rule for the www-data user to escalate privileges to root.) The code error is in gravity_DownloadBlocklistFromUrl in gravity.sh.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-11108
• https://frichetten.com/blog/cve-2020-11108-pihole-rce/
• https://github.com/Frichetten/CVE-2020-11108-PoC
• http://packetstormsecurity.com/files/157623/Pi-hole-4.4-Remote-Code-Execution.html
• http://packetstormsecurity.com/files/157624/Pi-hole-4.4-Remote-Code-Execution-Privilege-Escalation.html
• http://packetstormsecurity.com/files/157748/Pi-Hole-heisenbergCompensator-Blocklist-OS-Command-Execution.html
• http://packetstormsecurity.com/files/157839/Pi-hole-4.4.0-Remote-Code-Execution.html