GhostLock turns a fifteen-year-old rtmutex use-after-free into root in five seconds

CVE-2026-43499, dubbed GhostLock, is a use-after-free in rtmutex priority-inheritance code that has shipped since kernel 2.6.39 and is reachable by any unprivileged local process. The fix landed in 7.1, but two months after the public PoC, blind spots like RHEL 9 kernel-rt remain: check your version and block PI futexes in the meantime.