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’t need it. Lock yourself in and look over your sholder …
Fix
Linus Torvalds himself patched the kernel: Making sure you're not a bot!. We have to see on when we patch our supported kernels …
More info
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