bpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch()

{
  "id": "94ca346fcca065d8dac45cd1613bd485335aec6fa9319fbf3a967635d658b560",
  "url": "https://osv.dev/vulnerability/CVE-2026-74714",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch() reqsk_queue_hash_req() publishes a TCP_NEW_SYN_RECV request_sock onto the ehash chain, drops the bucket lock, and only afterwards sets rsk_refcnt to 3. Lockless readers such as __inet_lookup_established() handle this with refcount_inc_not_zero(), but bpf_iter_tcp_established_batch() uses plain sock_hold() while holding the bucket lock, on the assumption that the lock guarantees sk_refcnt > 0. That assumption does not hold for request_sock: CPU 0 CPU 1 ----- ----- tcp_conn_request() reqsk_queue_hash_req() inet_ehash_insert(req) spin_lock(bucket) __sk_nulls_add_node_rcu(req) // rsk_refcnt == 0 spin_unlock(bucket) bpf_iter_tcp_established_batch() spin_lock(bucket) sock_hold(req) <-- addition on 0 spin_unlock(bucket) refcount_set(&req->rsk_refcnt, 3) // clobbers saturated value which surfaces as: refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x48/0x90, CPU#1 Call Trace: bpf_iter_tcp_established_batch+0x14e/0x170 bpf_iter_tcp_batch+0x53/0x200 bpf_iter_tcp_seq_next+0x27/0x70 bpf_seq_read+0x107/0x410 vfs_read+0xb9/0x380 The iterator's stolen reference is lost when the publishing CPU's refcount_set() overwrites the count, leaving the socket one reference short. When the last legitimate owner drops its reference the reqsk is freed while still reachable, leading to use-after-free. This reproduces in second",
    "evidence": "osv:CVE-2026-74714",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.183",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.152",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.104",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.45",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.9",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-74714",
      "aliases": [
        "CVE-2026-74714"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
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                {
                  "fixed": "ddbe966b5d1fe212ada749bc3d0b410f1a7dea74"
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                {
                  "fixed": "7d2b60a4bc0499f62ff8520af6309bbe170882fd"
                },
                {
                  "fixed": "cefcbbe20846a45f9a7dae868f7ef1000953e2df"
                },
                {
                  "fixed": "97e74d3e45d653c07c2d406fc530a9bbe3df8396"
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                {
                  "fixed": "e5fd3f514e27db1f05fbd72ba615d74941e23c51"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74714.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.15.0"
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            {
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                  "introduced": "6.19.0"
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                {
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              ]
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74714.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.284397537Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/7d2b60a4bc0499f62ff8520af6309bbe170882fd",
        "https://git.kernel.org/stable/c/97e74d3e45d653c07c2d406fc530a9bbe3df8396",
        "https://git.kernel.org/stable/c/cc0295f89296ed351fc4b0b48fee887ba02c5d24",
        "https://git.kernel.org/stable/c/cefcbbe20846a45f9a7dae868f7ef1000953e2df",
        "https://git.kernel.org/stable/c/ddbe966b5d1fe212ada749bc3d0b410f1a7dea74",
        "https://git.kernel.org/stable/c/e5fd3f514e27db1f05fbd72ba615d74941e23c51",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74714.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-74714",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74714.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-74714",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 497287,
  "published_at": "2026-08-22T15:33:09.643+00:00"
}