[ALERT] ssh-keysign-pwn, unprivileged users are able to read root-owned files (opens in new tab)

Read root-owned files as an unprivileged user. Pre-31e62c2ebbfd kernels (everything in stable as of 2026-05-14). The bug __ptrace_may_access() skips the dumpable check when task->mm == NULL. do_exit() runs exit_mm() before exit_files() — no mm, fds still there. pidfd_getfd(2) succeeds in that window when the caller’s uid matches the target’s. Reported by Qualys, fixed by Linus 2026-05-14. Jann Horn flagged the FD-theft shape in October 2020. Six years. Mitigation Don’t run your PC if you don’...