CVE-2026-64422 (GCVE-0-2026-64422)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:51 – Updated: 2026-09-08 08:50
VLAI
Title
net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes
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.
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf , < f0d88a4cd03affff6c08adf6c63964e235aede43 (git)
Affected: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf , < 27ddf4486c7dbf5bdd393fa8bef6b67179796d98 (git)
Affected: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf , < 782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae (git)
Affected: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf , < e81f805824a8109504fce090641b17d135b48cd1 (git)
Affected: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf , < 99206ce2244f8a3ed64298d0667c9055845a5dc7 (git)
Affected: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf , < bbae351c0f32f7c200249e4aa6561b2b419dcf69 (git)
Affected: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf , < a094ac95d3b69adfa1676eb9c8eae6835d4f1671 (git)
Affected: 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf , < efb8763d7bbb40cff4cc55a6b62c3095a038149c (git)
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Linux Linux Affected: 2.6.24
Unaffected: 0 , < 2.6.24 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.212 , ≤ 5.15.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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    "datePublished": "2026-07-25T08:51:00.671Z",
    "dateReserved": "2026-07-19T15:36:31.787Z",
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      "date": "2026-09-20",
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      "percentile": "0.03303"
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      "cve": "CVE-2026-64422",
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      "product_status:known_affected": "1",
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      "status": "final",
      "title": "net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64422.json",
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                "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
                "vendor": "Siemens",
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                    "version": "V3.1.6",
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            "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
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        "cveTags": [],
        "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."
          }
        ],
        "id": "CVE-2026-64422",
        "lastModified": "2026-09-08T09:18:19.287",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.1,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "NONE",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
                "version": "3.1"
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              "exploitabilityScore": 1.8,
              "impactScore": 5.2,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
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        "published": "2026-07-25T10:17:26.213",
        "references": [
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
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            "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
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        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-190"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
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    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-29T14:07:36+00:00",
      "cve": "CVE-2026-64422",
      "id": "CVE-2026-64422",
      "initial_release_date": "2026-07-25T00:00:00+00:00",
      "product_status:known_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64422.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-15T01:49:11Z",
      "cve": "CVE-2026-64422",
      "id": "CVE-2026-64422",
      "initial_release_date": "2026-07-25T15:59:38Z",
      "product_status:known_affected": "376",
      "product_status:recommended": "4",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64422",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64422.json",
      "version": "8"
    }
  }
}



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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.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.