Froxlor 2.3.10 and earlier contain a time-of-check time-of-use (TOCTOU) race condition in the SSH…

Why it is Yellow

• CVSS 7.8 high

References

• https://github.com/froxlor/froxlor/security/advisories/GHSA-927x-9jfh-mq42
• https://www.vulncheck.com/advisories/froxlor-before-2.3.12-privilege-escalation-via-ssh-key-sync

Original description

Froxlor 2.3.10 and earlier contain a time-of-check time-of-use (TOCTOU) race condition in the SSH key synchronization cron (lib/Froxlor/Cron/System/SshKeys.php, SshKeys::generateFiles). The containment/symlink validation performed by FileDir::makeCorrectDir()/makeCorrectFile() is done only at check time; the live filesystem path is re-resolved as root at write time (file_put_contents with FILE_APPEND|LOCK_EX, followed by chmod/chown/chgrp), with a database round-trip and file reads in between, and no path or file-descriptor pinning (no O_NOFOLLOW or openat2(RESOLVE_NO_SYMLINKS)). On installations where the non-default setting system.allow_customer_shell=1 grants customers local shell access, a customer can atomically swap their ~/.ssh directory for a symlink after the check and before the write, causing the root-run cron to append the customer's public key to /root/.ssh/authorized_keys and to chown /root/.ssh to the customer, resulting in full root compromise of the panel host. The cron re-runs on every interval, allowing unlimited attempts. This is a residual race that bypasses the check-time fix introduced for GHSA-mq5v-... . The issue is fixed in Froxlor 2.3.12.