CVE-2026-98043
Received Received - Intake

BPF Pointer Arithmetic Null Pointer Dereference

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: bpf: Don't infer non-NULL from a pointer with an unbounded offset reg_not_null() decides that a register holds a non-NULL value by looking at its type alone. For pointer types that allow arithmetic the type only guarantees a non-NULL base, in case of an unbound offset the runtime offset value might still add up to NULL. Consider the followng program: r6 = bpf_map_lookup_elem(map, &0); /* present */ if (r6 == 0) return 0; r7 = bpf_map_lookup_elem(map, &1); /* absent, NULL at runtime */ r8 = r7; r8 -= r6; /* pointer - pointer: unknown scalar, -r6 */ r8 <<= 1; r8 >>= 1; /* any non-negative offset is accepted by */ /* check_reg_sane_offset_ptr() */ r6 += r8; /* verifier: map value; runtime: zero */ if (r7 != r6) return 0; *(u8 *)(r7 + 0); /* r7 is inferred non-NULL, both are zero */ At runtime both registers are zero, the comparison is true and the load faults with NULL pointer dereference. Require the offset to be within +-BPF_MAX_VAR_OFF in reg_not_null().

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-98043
EUVD
EUVD-2026-86696

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a flaw in the BPF (Berkeley Packet Filter) verifier. The issue occurs when the verifier incorrectly assumes a pointer is non-NULL based on its type, even when arithmetic operations could result in a NULL pointer. This can lead to a NULL pointer dereference at runtime, causing crashes or potential security issues.

Detection Guidance

This vulnerability is specific to the Linux kernel's BPF (Berkeley Packet Filter) implementation. Detection requires checking the kernel version and BPF-related components. Use commands like 'uname -r' to check the kernel version and 'lsmod | grep bpf' to verify BPF module status. Monitor kernel logs for BPF-related errors or crashes.

Impact Analysis

If exploited, this vulnerability could allow an attacker to trigger a NULL pointer dereference in the Linux kernel, leading to system crashes or denial-of-service conditions. It may also enable privilege escalation if combined with other vulnerabilities, though exploitation requires specific BPF program conditions.

Mitigation Strategies

Apply the latest kernel security patches from your Linux distribution. If patches are unavailable, consider disabling BPF functionality if not required. Update BPF-related tools and libraries. Monitor vendor advisories for updates and mitigations.

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