Bug 2541244 (CVE-2026-98039)

Summary: CVE-2026-98039 kernel: bpf: Require MEM_PERCPU for percpu kptr stores
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's BPF (Berkeley Packet Filter) verifier. The verifier improperly validates pointer types when storing values into per-CPU map fields, allowing standard memory allocations or kernel pointers to be accepted as per-CPU data. A local user with permissions to load BPF programs could exploit this vulnerability to perform arbitrary kernel memory reads and writes, potentially resulting in privilege escalation or a Denial of Service (DoS) caused by a system crash.
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Description OSIDB Bzimport 2026-09-25 11:09:29 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf: Require MEM_PERCPU for percpu kptr stores

map_kptr_match_type() treats perm_flags as the set of register type flags
that a kptr field permits. Adding MEM_PERCPU to that set for
BPF_KPTR_PERCPU does not require the source register to carry it, however.
The subset test consequently accepts both a plain bpf_obj_new() allocation
and a referenced kernel pointer into a __percpu_kptr map field.

Loads from the field are always marked MEM_PERCPU. Consumers then treat the
stored value as the cookie returned by bpf_percpu_obj_new(): per-CPU pointer
helpers relocate it, and map teardown selects the per-CPU free path. A plain
allocation can therefore provide an arbitrary kernel read/write, while a
kernel pointer can be relocated into an invalid address or sent through a
missing destructor.

Require the source MEM_PERCPU flag to match the destination field kind.
This preserves valid bpf_percpu_obj_new() stores and rejects both the
program-BTF and kernel-BTF variants.
Comment 1 Keith Grant 2026-09-28 22:44:14 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98039.mbox