CVE-2026-63926 (GCVE-0-2026-63926)
Vulnerability from cvelistv5
Published
2026-07-19 14:55
Modified
2026-08-05 12:37
Severity ?
8.4 (High) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: sockmap: fix tail fragment offset in bpf_msg_push_data When bpf_msg_push_data() inserts data in the middle of a scatterlist entry, it splits the original entry into a left fragment and a right fragment. The right fragment offset is page-local, but the code advances it with `start`, which is the message-global insertion point. For inserts into a non-first SG entry, this over-advances the offset and leaves the split layout inconsistent. Advance the right fragment offset by the fragment-local delta, `start - offset`, which matches the length removed from the front of the original entry.
References
Impacted products
Vendor Product Version
Linux Linux Version: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28
Version: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28
Version: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28
Version: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28
Version: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28
Version: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28
Version: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28
Version: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/filter.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
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              "status": "affected",
              "version": "6fff607e2f14bd7c63c06c464a6f93b8efbabe28",
              "versionType": "git"
            },
            {
              "lessThan": "d81b323af2dcee47573907ccb89c0df9b45cb2e2",
              "status": "affected",
              "version": "6fff607e2f14bd7c63c06c464a6f93b8efbabe28",
              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "6fff607e2f14bd7c63c06c464a6f93b8efbabe28",
              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "6fff607e2f14bd7c63c06c464a6f93b8efbabe28",
              "versionType": "git"
            },
            {
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              "versionType": "git"
            },
            {
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              "status": "affected",
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            {
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            },
            {
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              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.20"
            },
            {
              "lessThan": "4.20",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.259",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.210",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.176",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.259",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.210",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.176",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.143",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.93",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.35",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.12",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: sockmap: fix tail fragment offset in bpf_msg_push_data\n\nWhen bpf_msg_push_data() inserts data in the middle of a scatterlist\nentry, it splits the original entry into a left fragment and a right\nfragment.\n\nThe right fragment offset is page-local, but the code advances it with\n`start`, which is the message-global insertion point. For inserts into a\nnon-first SG entry, this over-advances the offset and leaves the split\nlayout inconsistent.\n\nAdvance the right fragment offset by the fragment-local delta,\n`start - offset`, which matches the length removed from the front of the\noriginal entry."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached through the BPF sk_msg/sockmap send path (sendmsg \u2192 tcp_bpf_send_verdict \u2192 sk_psock_msg_verdict \u2192 bpf_msg_push_data), which requires local syscalls and BPF setup; per kernel CNA guidance, BPF/sockmap issues are scored as Local rather than Network.\nAC:L - An attacker who can load a sk_msg BPF program fully controls the insertion offset and can reliably build multi-fragment scatterlist messages (e.g., via large sendmsg/sendfile) to hit the non-first-entry split path; a public PoC demonstrates deterministic triggering without races or external victim state.\nPR:N - While direct exploitation requires CAP_NET_ADMIN+CAP_BPF to load sockmap/sk_msg programs (obtainable as PR:L via user namespaces), the highest-impact reasonable scenario is an unauthenticated remote client triggering a pre-deployed internet-facing kTLS/sockmap proxy whose sk_msg BPF calls bpf_msg_push_data during outbound processing, requiring no privileges on the victim host.\nUI:N - Exploitation requires no victim user interaction beyond normal network I/O to a service that already runs sockmap/sk_msg BPF; the attacker does not need the victim to mount filesystems, open files, or take other deliberate actions.\nS:U - Impact is kernel heap memory corruption within the same kernel security authority (privilege escalation, memory disclosure, or crash), not a cross-boundary escape such as VM guest-to-host or IOMMU bypass.\nC:H - The incorrect rsge.offset over-advances the page-local offset for non-first scatterlist fragments, causing out-of-bounds reads when subsequent helpers (e.g., bpf_msg_pull_data via sg_virt/memcpy) or the TCP send path consume the corrupted entry; the public PoC shows a 32,752-byte OOB read/UAF.\nI:H - Scatterlist metadata corruption produces inconsistent length/offset pairs that can drive out-of-bounds kernel memory access and is a standard heap corruption primitive potentially weaponizable for arbitrary write or control-flow hijack, not merely a bounded data error.\nA:H - Corrupted scatterlist state can cause kernel oops/panic from out-of-bounds page access (as shown in the PoC KASAN trace) or destabilize subsequent sk_msg/TCP/kTLS transmit processing, resulting in denial of service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:37:21.277Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f14609d8146707452e0822f3c8154674ce677251"
        },
        {
          "url": "https://git.kernel.org/stable/c/d81b323af2dcee47573907ccb89c0df9b45cb2e2"
        },
        {
          "url": "https://git.kernel.org/stable/c/aeb95146848d12206e1b2cfacd4f40e21ce81d94"
        },
        {
          "url": "https://git.kernel.org/stable/c/96b72672ce849a1402730238e64d9b20bf06a96d"
        },
        {
          "url": "https://git.kernel.org/stable/c/3075c21d2d76c0067f4a382765b43d6cc10470f1"
        },
        {
          "url": "https://git.kernel.org/stable/c/5e19028667963fb371ebb00cecc2a473ef92056b"
        },
        {
          "url": "https://git.kernel.org/stable/c/63f64a510c7917658ddf4d073ece73914ee25346"
        },
        {
          "url": "https://git.kernel.org/stable/c/f72eed9b84fb771019a955908132410a9ba9ea3f"
        }
      ],
      "title": "bpf: sockmap: fix tail fragment offset in bpf_msg_push_data",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63926",
    "datePublished": "2026-07-19T14:55:27.154Z",
    "dateReserved": "2026-07-19T07:54:57.021Z",
    "dateUpdated": "2026-08-05T12:37:21.277Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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