CVE-2026-64422 (GCVE-0-2026-64422)
Vulnerability from cvelistv5
Published
2026-07-25 08:51
Modified
2026-08-17 04:55
Severity ?
7.1 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes Reject invalid `net.ipv4.tcp_reordering` values before they reach TCP socket state. The sysctl is stored as an `int` but copied into the `u32` `tp->reordering` field for new sockets, so negative writes wrap to large values. With `tcp_mtu_probing=2`, the wrapped value can overflow the `tcp_mtu_probe()` size calculation and drive the MTU probing path into an out-of-bounds read. Route `tcp_reordering` writes through `proc_dointvec_minmax()` and require it to be at least 1. Also require `tcp_max_reordering` to be at least 1 so the configured maximum cannot become negative either. When registering the table for a non-init network namespace, relocate `extra2` pointers that refer into `init_net.ipv4` so the `tcp_reordering` upper bound follows that namespace's `tcp_max_reordering`. Harden `tcp_mtu_probe()` itself by computing `size_needed` as `u64`. This keeps the send queue and window checks from being bypassed through signed integer overflow.
References
Impacted products
Vendor Product Version
Linux Linux Version: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf
Version: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf
Version: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf
Version: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf
Version: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf
Version: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf
Version: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf
Version: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/sysctl_net_ipv4.c",
            "net/ipv4/tcp_output.c"
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          "vendor": "Linux",
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              "version": "0",
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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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\nnet: ipv4: bound TCP reordering sysctl writes and MTU probe sizes\n\nReject invalid `net.ipv4.tcp_reordering` values before they reach TCP\nsocket state. The sysctl is stored as an `int` but copied into the\n`u32` `tp-\u003ereordering` field for new sockets, so negative writes wrap\nto large values.\n\nWith `tcp_mtu_probing=2`, the wrapped value can overflow the\n`tcp_mtu_probe()` size calculation and drive the MTU probing path into\nan out-of-bounds read. Route `tcp_reordering` writes through\n`proc_dointvec_minmax()` and require it to be at least 1. Also require\n`tcp_max_reordering` to be at least 1 so the configured maximum cannot\nbecome negative either.\n\nWhen registering the table for a non-init network namespace, relocate\n`extra2` pointers that refer into `init_net.ipv4` so the\n`tcp_reordering` upper bound follows that namespace\u0027s\n`tcp_max_reordering`.\n\nHarden `tcp_mtu_probe()` itself by computing `size_needed` as `u64`.\nThis keeps the send queue and window checks from being bypassed through\nsigned integer overflow."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The attacker must locally write the per-network-namespace TCP sysctls and exercise a TCP socket; remote packets alone cannot introduce the invalid signed value.\nAC:L - The attacker can set both tcp_reordering and tcp_mtu_probing=2, establish an attacker-controlled TCP connection, grow its congestion window, and control queued data and receiver-window conditions.\nPR:L - Writes require CAP_NET_ADMIN in the network namespace\u2019s owning user namespace, which an unprivileged user can obtain by creating user and network namespaces on systems permitting unprivileged user namespaces.\nUI:N - The attacker can configure the namespace and trigger MTU probing using their own TCP endpoints without any victim action.\nS:U - The vulnerable TCP implementation and the affected kernel memory and availability remain within the Linux kernel\u2019s security authority.\nC:H - The overflow bypasses send-queue validation and causes an out-of-bounds kernel-memory read through an invalid skb traversal, potentially exposing sensitive kernel data.\nI:N - The established primitive is an out-of-bounds read and malformed skb state; the affected path provides no demonstrated out-of-bounds write or other data-modification primitive.\nA:H - The invalid skb access and inconsistent payload geometry can cause an OOPS, BUG, or kernel panic, and an attacker can trigger the path repeatedly."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:55:22.159Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f0d88a4cd03affff6c08adf6c63964e235aede43"
        },
        {
          "url": "https://git.kernel.org/stable/c/27ddf4486c7dbf5bdd393fa8bef6b67179796d98"
        },
        {
          "url": "https://git.kernel.org/stable/c/782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae"
        },
        {
          "url": "https://git.kernel.org/stable/c/e81f805824a8109504fce090641b17d135b48cd1"
        },
        {
          "url": "https://git.kernel.org/stable/c/99206ce2244f8a3ed64298d0667c9055845a5dc7"
        },
        {
          "url": "https://git.kernel.org/stable/c/bbae351c0f32f7c200249e4aa6561b2b419dcf69"
        },
        {
          "url": "https://git.kernel.org/stable/c/a094ac95d3b69adfa1676eb9c8eae6835d4f1671"
        },
        {
          "url": "https://git.kernel.org/stable/c/efb8763d7bbb40cff4cc55a6b62c3095a038149c"
        }
      ],
      "title": "net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64422",
    "datePublished": "2026-07-25T08:51:00.671Z",
    "dateReserved": "2026-07-19T15:36:31.787Z",
    "dateUpdated": "2026-08-17T04:55:22.159Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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