CVE-2026-31413 (GCVE-0-2026-31413)
Vulnerability from cvelistv5
Published
2026-04-12 05:36
Modified
2026-08-05 12:22
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR maybe_fork_scalars() is called for both BPF_AND and BPF_OR when the source operand is a constant. When dst has signed range [-1, 0], it forks the verifier state: the pushed path gets dst = 0, the current path gets dst = -1. For BPF_AND this is correct: 0 & K == 0. For BPF_OR this is wrong: 0 | K == K, not 0. The pushed path therefore tracks dst as 0 when the runtime value is K, producing an exploitable verifier/runtime divergence that allows out-of-bounds map access. Fix this by passing env->insn_idx (instead of env->insn_idx + 1) to push_stack(), so the pushed path re-executes the ALU instruction with dst = 0 and naturally computes the correct result for any opcode.
References
Impacted products
Vendor Product Version
Linux Linux Version: dea9989a3f3961faede93752cd81eb5a9514d911
Version: 4c122e8ae14950cf6b59d208fc5160f7c601e746
Version: e52567173ba86dbffb990595fbe60e2e83899372
Version: bffacdb80b93b7b5e96b26fad64cc490a6c7d6c7
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   Linux Linux Version: 6.12.75   ≤
Version: 6.18.16   ≤
Version: 6.19.6   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "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": "342aa1ee995ef5bbf876096dc3a5e51218d76fa4",
              "status": "affected",
              "version": "dea9989a3f3961faede93752cd81eb5a9514d911",
              "versionType": "git"
            },
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              "status": "affected",
              "version": "4c122e8ae14950cf6b59d208fc5160f7c601e746",
              "versionType": "git"
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              "status": "affected",
              "version": "e52567173ba86dbffb990595fbe60e2e83899372",
              "versionType": "git"
            },
            {
              "lessThan": "c845894ebd6fb43226b3118d6b017942550910c5",
              "status": "affected",
              "version": "bffacdb80b93b7b5e96b26fad64cc490a6c7d6c7",
              "versionType": "git"
            }
          ]
        },
        {
          "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": "6.12.80",
              "status": "affected",
              "version": "6.12.75",
              "versionType": "semver"
            },
            {
              "lessThan": "6.18.21",
              "status": "affected",
              "version": "6.18.16",
              "versionType": "semver"
            },
            {
              "lessThan": "6.19.11",
              "status": "affected",
              "version": "6.19.6",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.80",
                  "versionStartIncluding": "6.12.75",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.21",
                  "versionStartIncluding": "6.18.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.11",
                  "versionStartIncluding": "6.19.6",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR\n\nmaybe_fork_scalars() is called for both BPF_AND and BPF_OR when the\nsource operand is a constant.  When dst has signed range [-1, 0], it\nforks the verifier state: the pushed path gets dst = 0, the current\npath gets dst = -1.\n\nFor BPF_AND this is correct: 0 \u0026 K == 0.\nFor BPF_OR this is wrong:    0 | K == K, not 0.\n\nThe pushed path therefore tracks dst as 0 when the runtime value is K,\nproducing an exploitable verifier/runtime divergence that allows\nout-of-bounds map access.\n\nFix this by passing env-\u003einsn_idx (instead of env-\u003einsn_idx + 1) to\npush_stack(), so the pushed path re-executes the ALU instruction with\ndst = 0 and naturally computes the correct result for any opcode."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable verifier path is reached through the local bpf() syscall during BPF_PROG_LOAD, not through a remote protocol. A plausible path is an attacker-supplied socket-filter BPF program using attacker-created maps.\nAC:L - The attacker controls the BPF bytecode, map layout, and scalar values needed to trigger the verifier/runtime divergence. There is no race or external condition beyond attacker control.\nPR:L - Exploitation requires a local user able to load BPF programs, which can be a basic unprivileged user where unprivileged BPF is enabled or a delegated BPF capability path exists. It does not inherently require real init-namespace root for the vulnerable verifier logic.\nUI:N - No victim action is required after the attacker loads and runs the crafted BPF program. The trigger is fully under the local attacker\u0027s control.\nS:U - This is a standard kernel privilege-escalation style BPF verifier flaw within the same host kernel security authority. It does not cross a VM, hypervisor, or IOMMU boundary.\nC:H - The verifier/runtime divergence allows out-of-bounds map-value reads, which can expose adjacent kernel heap data and be developed into broader kernel memory disclosure. BPF verifier OOB map-access bugs are commonly exploitable as kernel read primitives.\nI:H - The same incorrect bounds reasoning can be applied to writes through map-value pointers, enabling out-of-bounds kernel heap corruption. That is sufficient for arbitrary kernel memory modification or code execution in a defensible worst case.\nA:H - Out-of-bounds BPF memory access can corrupt kernel memory or fault the kernel, causing an oops, panic, or hang. Even failed exploitation can be repeatedly triggered by the local attacker."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:22:19.762Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/342aa1ee995ef5bbf876096dc3a5e51218d76fa4"
        },
        {
          "url": "https://git.kernel.org/stable/c/58bd87d0e69204dbd739e4387a1edb0c4b1644e7"
        },
        {
          "url": "https://git.kernel.org/stable/c/d13281ae7ea8902b21d99d10a2c8caf0bdec0455"
        },
        {
          "url": "https://git.kernel.org/stable/c/c845894ebd6fb43226b3118d6b017942550910c5"
        }
      ],
      "title": "bpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31413",
    "datePublished": "2026-04-12T05:36:14.632Z",
    "dateReserved": "2026-03-09T15:48:24.087Z",
    "dateUpdated": "2026-08-05T12:22:19.762Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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