Froxlor before 2.3.12 does not restrict or escape the system.letsencryptchallengepath setting…

Why it is Amber

• CVSS 9.1 critical

References

• https://github.com/froxlor/froxlor/security/advisories/GHSA-3w4g-cmpj-rj42
• https://www.vulncheck.com/advisories/froxlor-before-2.3.12-command-injection-via-letsencryptchallengepath

Original description

Froxlor before 2.3.12 does not restrict or escape the system.letsencryptchallengepath setting: unlike sibling settings hardened in GHSA-33mp, the field has no string_regexp or required_otp guard, and its value is concatenated unescaped into the acme.sh command line built in lib/Froxlor/Cron/Http/LetsEncrypt/AcmeSh.php and executed by the root cron via FileDir::safe_exec. Because safe_exec only blacklists shell metacharacters such as ; | & > < \ $ ~ ?, spaces and quotes survive and the value is word-split into additional acme.sh arguments. An administrator, or any actor able to write settings (for example through the settings-import API), can therefore inject acme.sh options such as --renew-hook, --pre-hook or --post-hook to obtain arbitrary command execution as root at the next Let's Encrypt cron run, or use --config-home/--cert-home for arbitrary file writes. Versions up to and including 2.3.10 are affected; the issue is fixed in 2.3.12.