CVE-2026-98043 (GCVE-0-2026-98043)
Vulnerability from cvelistv5
Published
2026-09-25 10:23
Modified
2026-10-21 12:54
Severity ?
Summary
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().
References
Impacted products
Vendor Product Version
Linux Linux Version: cac616db39c207dc63465a4e05c6ce0e60b2cce4
Version: cac616db39c207dc63465a4e05c6ce0e60b2cce4
Version: cac616db39c207dc63465a4e05c6ce0e60b2cce4
Version: cac616db39c207dc63465a4e05c6ce0e60b2cce4
Version: cac616db39c207dc63465a4e05c6ce0e60b2cce4
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{
  "containers": {
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        {
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          "product": "Linux",
          "programFiles": [
            "kernel/bpf/verifier.c"
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          "product": "Linux",
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          "vendor": "Linux",
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              "version": "0",
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              "status": "unaffected",
              "version": "6.18.57",
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              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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              "negate": false,
              "operator": "OR"
            }
          ]
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Don\u0027t infer non-NULL from a pointer with an unbounded offset\n\nreg_not_null() decides that a register holds a non-NULL value by\nlooking at its type alone. For pointer types that allow arithmetic the\ntype only guarantees a non-NULL base, in case of an unbound offset\nthe runtime offset value might still add up to NULL.\nConsider the followng program:\n\n  r6 = bpf_map_lookup_elem(map, \u00260);  /* present */\n  if (r6 == 0) return 0;\n  r7 = bpf_map_lookup_elem(map, \u00261);  /* absent, NULL at runtime */\n  r8 = r7;\n  r8 -= r6;     /* pointer - pointer: unknown scalar, -r6 */\n  r8 \u003c\u003c= 1;\n  r8 \u003e\u003e= 1;     /* any non-negative offset is accepted by */\n                /* check_reg_sane_offset_ptr() */\n  r6 += r8;     /* verifier: map value;    runtime: zero  */\n  if (r7 != r6) return 0;\n  *(u8 *)(r7 + 0);  /* r7 is inferred non-NULL, both are zero */\n\nAt runtime both registers are zero, the comparison is true and the\nload faults with NULL pointer dereference.\n\nRequire the offset to be within +-BPF_MAX_VAR_OFF in reg_not_null()."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:54:11.750Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/8b414dbe97fcefd116e5a620c3bd9993014aa4ce"
        },
        {
          "url": "https://git.kernel.org/stable/c/019d845a08b8ccfe8eefaaf4bca6870f2b8c58ae"
        },
        {
          "url": "https://git.kernel.org/stable/c/65bea674f43c09c0eda033a140dfac6a2842a19f"
        },
        {
          "url": "https://git.kernel.org/stable/c/cb6642048739bf4ee5aa09fe465511f1e87caa63"
        },
        {
          "url": "https://git.kernel.org/stable/c/67b529f521a6676cdfc78b91b0217d7eaa84216b"
        }
      ],
      "title": "bpf: Don\u0027t infer non-NULL from a pointer with an unbounded offset",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98043",
    "datePublished": "2026-09-25T10:23:54.865Z",
    "dateReserved": "2026-09-25T10:19:56.071Z",
    "dateUpdated": "2026-10-21T12:54:11.750Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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