CVE-2026-98149 bpf: Fix percpu map update indexing with sparse CPU IDs
A Linux kernel bug in BPF per-CPU map updates causes out-of-bounds reads when CPU IDs are sparse, potentially allowing local attackers to read memory or escalate privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98149?
CVE-2026-98149 is a high-severity memory corruption vulnerability in Linux kernel, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix percpu map update indexing with sparse CPU IDs
Per-CPU array, hash, and cgroup storage map updates without BPF_F_CPU or BPF_F_ALL_CPUS use a value buffer whose per-CPU slots are packed in possible-CPU order. The buffer is sized as:
round_up(value_size, 8) * num_possible_cpus()
The update paths iterate over possible CPUs, but use the logical CPU ID to calculate the source offset:
value + size * cpu
This only works when possible CPU IDs are contiguous starting at zero.
For example, with a possible CPU mask of 0,2-3, the buffer contains three slots corresponding to CPUs 0, 2, and 3. CPU2 is therefore expected to use slot 1 and CPU3 slot 2. Instead, the current code uses slots 2 and 3 respectively, causing incorrect per-CPU values and an out-of-bounds read from the update buffer for CPU3.
The corresponding lookup paths already use a dense offset while iterating over possible CPUs. Do the same for the array, hash, and cgroup storage update paths, advancing the source offset once for each possible CPU. BPF_F_ALL_CPUS continues to use the same value for every CPU.
Weakness: CWE-125
Which versions are affected by CVE-2026-98149?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-98149?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-98149 being exploited?
There is no known exploitation of CVE-2026-98149 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2026-98149, GHSA-hwjh-c457-8mjm, UBUNTU-CVE-2026-98149.