MediumOS hardeningBLWK-KERNEL-011

Symlink following protection is disabled

What this means

fs.protected_symlinks is 0 — a process can follow a symlink in a world-writable sticky directory (like /tmp) even when it doesn't own the link, a long-standing local-privilege-escalation and file-clobbering primitive.

How to fix it

Set fs.protected_symlinks=1 via /etc/sysctl.d/ and run sysctl --system.

Check it yourself

Run a scan and look for BLWK-KERNEL-011 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:

protected_symlinks == 0

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

References

• CIS Benchmark 1.5.8
• MITRE ATT&CK T1068

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