MediumOS hardeningBLWK-KERNEL-007

perf_event_paranoid allows unprivileged kernel profiling

What this means

kernel.perf_event_paranoid is ‹perf event paranoid›, below 2 — the perf_event_open() syscall is a documented side-channel and kernel-address-disclosure vector, and several real privilege-escalation exploits have used it once accessible to unprivileged users.

How to fix it

Set kernel.perf_event_paranoid=2 (or higher) via /etc/sysctl.d/ and run sysctl --system.

Check it yourself

Run a scan and look for BLWK-KERNEL-007 in the results:

bulwark scan

Installed the standalone CLI package instead of the app? The command is bulwarkctl.

How Bulwark decides

Bulwark reads sysctl_kernel and reports this check when:

perf_event_paranoid < 2

If a value can't be read, Bulwark reports the check as undetermined rather than passing it. View the rule source.

References

• CIS Benchmark 1.5.5

Related checks

• Cron entry runs a downloader piped to a shell · BLWK-ACCT-001
• Password maximum age is excessively long · BLWK-ACCT-002
• Password minimum age is zero · BLWK-ACCT-003
• Password hashing rounds are not explicitly configured · BLWK-ACCT-004
• Default UMASK is not explicitly configured · BLWK-ACCT-005
• A sensitive system file is world-writable · BLWK-FS-001