CVE-2026-98040

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Mark the zero register precise for a register-form NULL check check_cond_jmp_op() accepts "if rA <op> rB" as a NULL check for a nullable pointer rA when rB is a scalar known to be zero, lifts PTR_MAYBE_NULL from rA in the corresponding branch and does not mark rB precise. Consider the following program: r0 = bpf_get_prandom_u32(); r6 = 1; /* the r6 == 0 path is explored first */ if (r0 == 0) goto 1f; r6 = 0; 1: r0 = bpf_map_lookup_elem(map, &0); /* absent, NULL at runtime */ if (r0 == r6) goto 2f; /* taken as a NULL check for r0 */ *(u8 *)(r0 + 0); /* verifier: map value; runtime: zero */ 2: return 0; The r6 == 0 path is explored first and the dereference is accepted. The r6 == 1 path is pruned at the checkpoint recorded for (1), so the comparison is never verified with a non-zero r6. At runtime a failed lookup returns NULL, NULL != 1 takes the non-NULL edge and the program dereferences a pointer that is zero.

Severity

Not scored

CVSS score

Not available

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-25 11:17:32.773000

Last modified

2026-10-19 10:17:57.910000

View original CVE JSON

{
  "id": "CVE-2026-98040",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-25T11:17:32.773",
  "lastModified": "2026-10-19T10:17:57.910",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Mark the zero register precise for a register-form NULL check\n\ncheck_cond_jmp_op() accepts \"if rA <op> rB\" as a NULL check for a\nnullable pointer rA when rB is a scalar known to be zero,\nlifts PTR_MAYBE_NULL from rA in the corresponding branch and does not\nmark rB precise. Consider the following program:\n\n  r0 = bpf_get_prandom_u32();\n  r6 = 1;                  /* the r6 == 0 path is explored first */\n  if (r0 == 0) goto 1f;\n  r6 = 0;\n1:\n  r0 = bpf_map_lookup_elem(map, &0);  /* absent, NULL at runtime */\n  if (r0 == r6) goto 2f;   /* taken as a NULL check for r0       */\n  *(u8 *)(r0 + 0);         /* verifier: map value; runtime: zero */\n2:\n  return 0;\n\nThe r6 == 0 path is explored first and the dereference is accepted.\nThe r6 == 1 path is pruned at the checkpoint recorded for (1),\nso the comparison is never verified with a non-zero r6. At runtime a\nfailed lookup returns NULL, NULL != 1 takes the non-NULL edge and the\nprogram dereferences a pointer that is zero."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "kernel/bpf/verifier.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "2f4cb53eed448c1aeb6f4b40cf9c810716d8218c",
              "lessThan": "ddca9a3b8833168dda3e62676648a636fb3f221c",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2f4cb53eed448c1aeb6f4b40cf9c810716d8218c",
              "lessThan": "6aed0134d3cda6382385a734ae0158eb7df6b142",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "kernel/bpf/verifier.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "7.1",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "7.1",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.7",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {},
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/6aed0134d3cda6382385a734ae0158eb7df6b142",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/ddca9a3b8833168dda3e62676648a636fb3f221c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}