FKIE_CVE-2026-64007

Vulnerability from fkie_nvd - Published: 2026-07-19 16:17 - Updated: 2026-07-20 15:17
Severity
9.8 (Critical) - CVSS:3.1/AV:N/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: netfilter: synproxy: refresh tcphdr after skb_ensure_writable synproxy_tstamp_adjust() rewrites the TCP timestamp option in place and then patches the TCP checksum via inet_proto_csum_replace4() on the caller-supplied tcphdr pointer. Both ipv4_synproxy_hook() and ipv6_synproxy_hook() obtain that pointer with skb_header_pointer() before calling in, so it may either alias skb->head directly or point at the caller's on-stack _tcph buffer. Between obtaining the pointer and using it, the function calls skb_ensure_writable(skb, optend), which on a cloned or non-linear skb invokes pskb_expand_head() and frees the old skb->head. After that point the cached th is stale: caller (ipv[46]_synproxy_hook) th = skb_header_pointer(skb, ..., &_tcph) synproxy_tstamp_adjust(skb, protoff, th, ...) skb_ensure_writable(skb, optend) pskb_expand_head() /* kfree(old skb->head) */ ... inet_proto_csum_replace4(&th->check, ...) /* writes into freed head, or into the caller's stack copy leaving the on-wire checksum stale */ The option bytes are written through skb->data and are fine; only the checksum update goes through th and so lands in the wrong place. The result is either a write into freed slab memory or a packet leaving with a checksum that does not match its payload. Fix by re-deriving th from skb->data + protoff immediately after skb_ensure_writable() succeeds, so the subsequent checksum update targets the linear, writable header.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/92170e6afe927ab2792a3f71902845789c8e31b1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9902a1058992de5d95656b64a3bd95c077f7ba2c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a91887a5b6ee4b98dfbf1db657ed2b879430149e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/af2c22ccb1f621aff487ff47a040e38e058541e7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c7f945f7da097245a2f8ed7775ce48421047ee96
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d3019c61799adc21811af4b521f11f3dc77f8e04
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dd206819f210522579010d889d45a9530bb494bc
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f0fea2b6d5453a11ad11713bbf37561b9b3a7edf
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_synproxy_core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "9902a1058992de5d95656b64a3bd95c077f7ba2c",
              "status": "affected",
              "version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
              "versionType": "git"
            },
            {
              "lessThan": "d3019c61799adc21811af4b521f11f3dc77f8e04",
              "status": "affected",
              "version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
              "versionType": "git"
            },
            {
              "lessThan": "dd206819f210522579010d889d45a9530bb494bc",
              "status": "affected",
              "version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
              "versionType": "git"
            },
            {
              "lessThan": "af2c22ccb1f621aff487ff47a040e38e058541e7",
              "status": "affected",
              "version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
              "versionType": "git"
            },
            {
              "lessThan": "c7f945f7da097245a2f8ed7775ce48421047ee96",
              "status": "affected",
              "version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
              "versionType": "git"
            },
            {
              "lessThan": "f0fea2b6d5453a11ad11713bbf37561b9b3a7edf",
              "status": "affected",
              "version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
              "versionType": "git"
            },
            {
              "lessThan": "a91887a5b6ee4b98dfbf1db657ed2b879430149e",
              "status": "affected",
              "version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
              "versionType": "git"
            },
            {
              "lessThan": "92170e6afe927ab2792a3f71902845789c8e31b1",
              "status": "affected",
              "version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_synproxy_core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.12"
            },
            {
              "lessThan": "3.12",
              "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"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: synproxy: refresh tcphdr after skb_ensure_writable\n\nsynproxy_tstamp_adjust() rewrites the TCP timestamp option in place\nand then patches the TCP checksum via inet_proto_csum_replace4() on\nthe caller-supplied tcphdr pointer.  Both ipv4_synproxy_hook() and\nipv6_synproxy_hook() obtain that pointer with skb_header_pointer()\nbefore calling in, so it may either alias skb-\u003ehead directly or\npoint at the caller\u0027s on-stack _tcph buffer.\n\nBetween obtaining the pointer and using it, the function calls\nskb_ensure_writable(skb, optend), which on a cloned or non-linear\nskb invokes pskb_expand_head() and frees the old skb-\u003ehead.  After\nthat point the cached th is stale:\n\n    caller (ipv[46]_synproxy_hook)\n      th = skb_header_pointer(skb, ..., \u0026_tcph)\n      synproxy_tstamp_adjust(skb, protoff, th, ...)\n        skb_ensure_writable(skb, optend)\n          pskb_expand_head()        /* kfree(old skb-\u003ehead) */\n        ...\n        inet_proto_csum_replace4(\u0026th-\u003echeck, ...)\n                                    /* writes into freed head, or\n                                       into the caller\u0027s stack copy\n                                       leaving the on-wire checksum\n                                       stale */\n\nThe option bytes are written through skb-\u003edata and are fine; only\nthe checksum update goes through th and so lands in the wrong\nplace.  The result is either a write into freed slab memory or a\npacket leaving with a checksum that does not match its payload.\n\nFix by re-deriving th from skb-\u003edata + protoff immediately after\nskb_ensure_writable() succeeds, so the subsequent checksum update\ntargets the linear, writable header."
    }
  ],
  "id": "CVE-2026-64007",
  "lastModified": "2026-07-20T15:17:01.940",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-19T16:17:40.407",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/92170e6afe927ab2792a3f71902845789c8e31b1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9902a1058992de5d95656b64a3bd95c077f7ba2c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a91887a5b6ee4b98dfbf1db657ed2b879430149e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/af2c22ccb1f621aff487ff47a040e38e058541e7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c7f945f7da097245a2f8ed7775ce48421047ee96"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d3019c61799adc21811af4b521f11f3dc77f8e04"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dd206819f210522579010d889d45a9530bb494bc"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f0fea2b6d5453a11ad11713bbf37561b9b3a7edf"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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