CVE-2023-0386

CVE-2023-0386 is an improper ownership management flaw (CWE-282) in the Linux kernel's OverlayFS subsystem: due to a user-namespace uid-mapping bug, a setuid file with file capabilities that is copied from a 'nosuid' mount into another mount can be executed as setuid without authorization. A local attacker with an ordinary low-privilege account can trigger the flaw simply by copying such a capable file, with no user interaction required. Successful exploitation yields local privilege escalation on the host, with high impact to confidentiality, integrity, and availability. Affected products include the Linux kernel, Ubuntu Linux, Debian Linux, and NetApp H-series appliance firmware (H300S, H410C, H410S, H500S, H700S); CISA's affected list names the Linux Kernel. The flaw is being actively exploited in the wild - CISA added it to the Known Exploited Vulnerabilities catalog on 2025-06-17, though ransomware use is listed as unknown.

What to do: Apply vendor-supplied fixed kernel updates from Canonical or Debian and reboot affected hosts so the patched kernel is loaded; NetApp H300S/H500S/H700S/H410S/H410C systems should install fixed firmware per NetApp's advisory. Because the flaw is in the CISA KEV catalog (added 2025-06-17), follow BOD 22-01 guidance: apply vendor mitigations or discontinue use where fixes are unavailable, prioritizing multi-user servers and any host with untrusted local accounts.