CVE-2026-98149

bpf: Fix percpu map update indexing with sparse CPU IDs

Published Sep 25, 2026 CVSS 3.1 · 7.8 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
History
Type Values Removed Values Added
CPEs cpe:2.3:o:linux:linux_kernel:7.3:rc1:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-125
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
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.
Title bpf: Fix percpu map update indexing with sparse CPU IDs
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 19, 2026, 9:14 AM
Reserved
Sep 25, 2026, 10:25 AM
Status
Analyzed
Published
Sep 25, 2026, 11:17 AM
Modified
Oct 21, 2026, 8:36 PM
Severity
Moderate
Public date
Sep 25, 2026, 12:00 AM