# CVE-2026-98043: bpf: Don't infer non-NULL from a pointer with an unbounded offset

CVE-2026-98043 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-98043, released October 2, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-98043
- Priority: Routine
- CVSS: 5.5 (Moderate)
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 25, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98043

## 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().

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2026-98043](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98043.md) | Oct 2, 2026 |
| Linux | linux Debian 14 | 7.2.7-1 | [DEBIAN-CVE-2026-98043](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98043.md) | Oct 2, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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