CVE-2024-42063

What it actually does

The vulnerability permits use of uninitialized stack memory as the "void *key" argument to BPF map lookup and delete helpers when the program executes in interpreter mode, allowing privileged BPF programs to access or propagate unpoisoned memory regions.

Why it matters to the business

Linux systems relying on eBPF for networking, security, or observability face elevated risk of kernel memory disclosure or crashes; the issue affects broad kernel deployments but carries low exploitation probability and no known ransomware usage.

How an attack unfolds

An attacker with CAP_BPF or equivalent privileges loads a crafted eBPF program that intentionally leaves stack memory uninitialized before calling map lookup or delete helpers; in interpreter mode the kernel does not mark the stack region, enabling the uninit value to reach internal map functions and potentially leak kernel data or trigger further undefined behavior. Named threat actors have referenced similar Linux kernel uninitialized-resource issues in espionage and financially motivated campaigns.

How to fix it

Upgrade the Linux kernel to a version containing commit b30f3197a6cd080052d5d4973f9a6b479fd9fff5 or later stable releases that apply the kmsan_unpoison_memory marking for BPF program stacks.

How to confirm the fix worked

Confirm the running kernel contains the referenced commit, rebuild with KMSAN enabled and re-test the original syzbot reproducer, and verify that map lookup/delete operations no longer report uninit-value bugs.

Typical attack path

1. Obtain privileges sufficient to load eBPF programs
2. Craft a BPF program that allocates stack space and passes an uninitialized pointer region to dev_map_lookup_elem or equivalent helpers
3. Load and attach the program in interpreter mode
4. Trigger map operations to observe or exploit the uninitialized memory
5. Escalate via disclosed kernel data or induce denial of service

How to detect it

Search kernel logs for KMSAN uninit-value reports involving __dev_map_lookup_elem, dev_map_lookup_elem, or bpf_map_lookup_elem; inspect audit logs for unexpected BPF program loads and correlate with process execution of bpftool or similar loaders.

What your security team should do

• Prioritize kernel updates on systems that permit unprivileged or low-privilege BPF loading
• Restrict BPF program loading via LSM or seccomp policies where eBPF is not required
• Monitor kernel update channels for backports of the fix into distribution kernels
• Audit existing eBPF programs for use of uninitialized stack regions passed to map helpers