CVE-2024-26618

What it actually does

Incorrect logic in arm64 sme_alloc() fails to detect existing storage when not flushing, causing unconditional new allocation that leaks prior memory and corrupts SME state for callers that reallocate vector lengths.

Why it matters to the business

Systems running affected arm64 kernels may experience memory leaks, process or kernel instability, or denial of service when applications exercise SME vector-length changes; urgency is low given absence from KEV and stable low EPSS over 947 days since publication.

How an attack unfolds

An attacker would need to trigger repeated SME allocation paths (for example by forcing vector-length changes in a process using SME) on an unpatched arm64 kernel; the resulting state corruption could be leveraged for further memory manipulation, though no public exploitation or named threat actors are known.

How to fix it

Upgrade to fixed kernel versions: Linux 6.1.140 or later, Debian 12/13 packages 6.1.7-1 or later, or apply commit f6421555dbd7cb3d4d70b69f33f998aaeca1e3b5; ensure callers of sme_alloc() that reallocate invoke sme_free() themselves before upgrade where source modification is required.

How to confirm the fix worked

Confirm kernel version matches or exceeds the listed fixed releases; review SME allocation paths in arch/arm64/kernel/sme.c for separated flush and existing-storage checks; test with workloads that change SME vector length.

Typical attack path

1. Identify or create arm64 process using SME instructions
2. Force repeated vector-length changes that invoke sme_alloc() without prior sme_free()
3. Trigger allocation path while storage already exists and flush is false
4. Observe or exploit resulting memory leak and corrupted SME context for privilege escalation or DoS

How to detect it

Review kernel logs for SME-related allocation warnings or OOM events on arm64; inspect process coredumps or memory profiles for unexpected SME context growth; no public exploit artifacts or threat-actor TTPs are associated with this issue.

What your security team should do

• Prioritize patching arm64 systems to the fixed kernel versions within standard change windows
• Monitor upstream stable branches for any backports to older LTS kernels still in use
• Add kernel version checks to vulnerability scanning and asset inventory