FKIE_CVE-2026-98040

Vulnerability from fkie_nvd - Published: 2026-09-25 11:17 - Updated: 2026-09-25 11:17
Severity
Summary
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6aed0134d3cda6382385a734ae0158eb7df6b142
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ddca9a3b8833168dda3e62676648a636fb3f221c
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/verifier.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "ddca9a3b8833168dda3e62676648a636fb3f221c",
              "status": "affected",
              "version": "2f4cb53eed448c1aeb6f4b40cf9c810716d8218c",
              "versionType": "git"
            },
            {
              "lessThan": "6aed0134d3cda6382385a734ae0158eb7df6b142",
              "status": "affected",
              "version": "2f4cb53eed448c1aeb6f4b40cf9c810716d8218c",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/verifier.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "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 \u003cop\u003e 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, \u00260);  /* 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."
    }
  ],
  "id": "CVE-2026-98040",
  "lastModified": "2026-09-25T11:17:32.773",
  "metrics": {},
  "published": "2026-09-25T11:17:32.773",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6aed0134d3cda6382385a734ae0158eb7df6b142"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ddca9a3b8833168dda3e62676648a636fb3f221c"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.