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().
Published: 2026-09-25
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Fri, 25 Sep 2026 18:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-690

Fri, 25 Sep 2026 10:30:00 +0000

Type Values Removed Values Added
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().
Title bpf: Don't infer non-NULL from a pointer with an unbounded offset
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-25T10:23:54.865Z

Reserved: 2026-09-25T10:19:56.071Z

Link: CVE-2026-98043

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-25T11:17:33.090

Modified: 2026-09-25T11:17:33.090

Link: CVE-2026-98043

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-25T18:15:16Z

Weaknesses

No weakness.