kill: 'kill -1' parsed as PID -1, sending SIGTERM to all processes (system crash / DoS)

kill -1 is incorrectly parsed as a positional pid = -1; combined with the default SIGTERM this calls kill(-1, SIGTERM), signaling nearly every process the caller can see. GNU kill recognizes -1/-9 as signals and reports "not enough arguments".

$ kill -1        # uutils: kill(-1, SIGTERM) -> mass termination / crash
$ kill -1        # GNU: kill: not enough arguments

Impact: a user running kill -1 mass-terminates processes, potentially crashing the system. Recommendation: parse -N as a signal number, and error with "not enough arguments" when no PID is given.

Remediation: Acknowledged by Canonical; fixed in commit cae94028.

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Reported by Zellic in the uutils coreutils Program Security Assessment (prepared for Canonical, Jan 20 2026), audited commit 3a07ffc5a9bd4c283e75afa548ba1f1957bad242. Finding 3.70. Credit: Zellic.