Impact A privilege escalation vulnerability existed in the Below service prior to v0.9.0 due to the creation of a world-writable directory at /var/log/below. This could have allowed local unprivileged users to escalate to root privileges through symlink attacks that manipulate files such as /etc/shadow.

Patches https://github.com/facebookincubator/below/commit/10e73a21d67baa2cd613ee92ce999cda145e1a83

This is included in version 0.9.0

Workarounds Change the permission on /var/log/below manually

References https://www.facebook.com/security/advisories/cve-2025-27591 https://www.cve.org/CVERecord?id=CVE-2025-27591