CVE-2024-26602

What it actually does

The vulnerability allows repeated high-frequency calls to sys_membarrier, which is expensive on some systems, leading to resource saturation and overall system slowdown without any serialization or rate limiting.

Why it matters to the business

Attackers with local access can degrade system performance across the machine, disrupting operations and availability for all users and workloads until mitigated.

How an attack unfolds

A local attacker invokes sys_membarrier in a tight loop at high frequency to trigger expensive operations repeatedly, saturating the system and causing broad slowdowns; no remote or privileged escalation is required beyond basic local execution.

How to fix it

Update to a Linux kernel version containing the fix that adds locking to serialize sys_membarrier accesses. For affected Mastodon deployments, apply the listed GIT commits: b31af34c9716338e4a32a62cc812d1ca59e88d15 or 7c8ca0c6d612329523fc4e468e82fc3e51634c1c.

How to confirm the fix worked

Confirm kernel version is updated beyond the vulnerable commit; test by attempting high-frequency sys_membarrier calls and verifying they are now serialized without causing saturation.

Typical attack path

1. Obtain local code execution on the affected Linux system
2. Repeatedly invoke sys_membarrier syscall in a high-frequency loop
3. Saturate system resources leading to widespread performance degradation

How to detect it

Review system logs and audit trails for unusually high rates of membarrier syscall invocations from user processes; correlate with performance degradation events.

What your security team should do

• Prioritize patching Linux kernel on all affected systems due to local DoS risk
• Monitor for unusual local process activity invoking membarrier syscalls at high rates
• Apply kernel updates immediately where local user access is possible