CVE-2026-80738 (GCVE-0-2026-80738)

Vulnerability from cvelistv5 – Published: 2026-09-03 08:21 – Updated: 2026-09-04 04:58
VLAI
Title
bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie accept a socket pointer 'sk' with argument type ARG_PTR_TO_BTF_ID_SOCK_COMMON. However, they access sk->sk_protocol without validating whether 'sk' represents a full socket. Fix this issue by checking sk->sk_state != TCP_LISTEN before inspecting sk->sk_protocol in both bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie. Since mini-sockets are never in the TCP_LISTEN state, the condition short-circuits and prevents dereferencing fullsock-specific fields.
Severity
7.3 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 399040847084a69f345e0a52fd62f04654e0fce3 , < 23f682083aa3fbc0c49667818efd6979a8bc5ac2 (git)
Affected: 399040847084a69f345e0a52fd62f04654e0fce3 , < 31a420a822ff92e2090bd5d65efe8e34e2d6d9b8 (git)
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Linux Linux Affected: 5.2
Unaffected: 0 , < 5.2 (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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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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              "lessThan": "23f682083aa3fbc0c49667818efd6979a8bc5ac2",
              "status": "affected",
              "version": "399040847084a69f345e0a52fd62f04654e0fce3",
              "versionType": "git"
            },
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              "status": "affected",
              "version": "399040847084a69f345e0a52fd62f04654e0fce3",
              "versionType": "git"
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          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/core/filter.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.2"
            },
            {
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "version": "7.2",
              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.9",
                  "versionStartIncluding": "5.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
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                  "vulnerable": true
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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: Check sk_state before sk_protocol in bpf_tcp_*_syncookie\n\nbpf_tcp_gen_syncookie and bpf_tcp_check_syncookie accept a socket pointer\n\u0027sk\u0027 with argument type ARG_PTR_TO_BTF_ID_SOCK_COMMON. However, they access\nsk-\u003esk_protocol without validating whether \u0027sk\u0027 represents a full socket.\n\nFix this issue by checking sk-\u003esk_state != TCP_LISTEN before inspecting\nsk-\u003esk_protocol in both bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie.\nSince mini-sockets are never in the TCP_LISTEN state, the condition\nshort-circuits and prevents dereferencing fullsock-specific fields."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.3,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The flaw is in bpf_tcp_gen_syncookie/bpf_tcp_check_syncookie BPF helpers invoked only from locally loaded and attached TC clsact or XDP programs via bpf(); per kernel CNA guidance BPF/tc paths are Local even when later triggered by ingress packets.\nAC:L - An attacker who loads the BPF program fully controls passing bpf_skc_lookup_tcp() results (request_sock/TCP_NEW_SYN_RECV or timewait sockets) into the syncookie helpers and can reliably trigger the bad sk_protocol read with crafted SYN/ACK traffic; no uncontrollable races or rare layout are required.\nPR:L - Exploitation requires bpf(BPF_PROG_LOAD) (CAP_BPF, obtainable in user namespaces) plus attaching TC/XDP hooks (CAP_NET_ADMIN via unshare -Urn); no init-namespace root is needed, matching CNA guidance for namespace-reachable net/BPF capabilities.\nUI:N - No victim mount, login, or cooperative action is required; once the attacker loads and attaches their BPF program, sending network packets from their own processes deterministically reaches the vulnerable helper on each matching lookup.\nS:U - Impact is confined to kernel heap disclosure/type confusion within the host kernel security domain; it does not cross VM, container runtime, IOMMU, or other security-authority boundaries.\nC:H - Casting a mini-socket to struct sock and reading sk_protocol performs a fixed-offset out-of-bounds read (~300+ bytes past request_sock/inet_timewait_sock) into adjacent slab memory, leaking kernel heap contents including pointers usable for further local exploitation.\nI:H - This is type confusion between ARG_PTR_TO_BTF_ID_SOCK_COMMON mini-sockets and full struct sock fields; per CNA guidance type confusion is rated High integrity impact even though the immediate bug is a read, because mis-typed socket pointers corrupt the kernel\u0027s object model.\nA:L - The primary impact is information disclosure; while the out-of-bounds u16 read usually stays within the slab page, reads near allocation boundaries or under KASAN can fault and oops the kernel, giving at least Low availability impact when uncertain."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-04T04:58:23.870Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/23f682083aa3fbc0c49667818efd6979a8bc5ac2"
        },
        {
          "url": "https://git.kernel.org/stable/c/31a420a822ff92e2090bd5d65efe8e34e2d6d9b8"
        }
      ],
      "title": "bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80738",
    "datePublished": "2026-09-03T08:21:53.143Z",
    "dateReserved": "2026-08-26T14:34:25.789Z",
    "dateUpdated": "2026-09-04T04:58:23.870Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-80738",
      "date": "2026-09-21",
      "epss": "0.00118",
      "percentile": "0.01962"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-04T01:06:21.000Z",
      "cve": "CVE-2026-80738",
      "id": "msrc_CVE-2026-80738",
      "initial_release_date": "2026-09-04T01:06:21.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-80738.json",
      "version": "1"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
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                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "net/core/filter.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
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                    "versionType": "git"
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                    "version": "5.2"
                  },
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                    "version": "0",
                    "versionType": "semver"
                  },
                  {
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                    "status": "unaffected",
                    "version": "7.1.9",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
                    "version": "7.2",
                    "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: Check sk_state before sk_protocol in bpf_tcp_*_syncookie\n\nbpf_tcp_gen_syncookie and bpf_tcp_check_syncookie accept a socket pointer\n\u0027sk\u0027 with argument type ARG_PTR_TO_BTF_ID_SOCK_COMMON. However, they access\nsk-\u003esk_protocol without validating whether \u0027sk\u0027 represents a full socket.\n\nFix this issue by checking sk-\u003esk_state != TCP_LISTEN before inspecting\nsk-\u003esk_protocol in both bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie.\nSince mini-sockets are never in the TCP_LISTEN state, the condition\nshort-circuits and prevents dereferencing fullsock-specific fields."
          }
        ],
        "id": "CVE-2026-80738",
        "lastModified": "2026-09-04T05:17:14.363",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "LOW",
                "baseScore": 7.3,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.5,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-09-03T13:06:12.910",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/23f682083aa3fbc0c49667818efd6979a8bc5ac2"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/31a420a822ff92e2090bd5d65efe8e34e2d6d9b8"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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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.

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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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