{
  "threat_severity" : "Important",
  "public_date" : "2026-07-19T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: netfilter: synproxy: refresh tcphdr after skb_ensure_writable",
    "id" : "2502361",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2502361"
  },
  "cvss3" : {
    "cvss3_base_score" : "7.0",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
    "status" : "verified"
  },
  "cwe" : "CWE-825",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nnetfilter: synproxy: refresh tcphdr after skb_ensure_writable\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->head directly or\npoint at the caller's on-stack _tcph buffer.\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->head.  After\nthat point the cached th is stale:\ncaller (ipv[46]_synproxy_hook)\nth = skb_header_pointer(skb, ..., &_tcph)\nsynproxy_tstamp_adjust(skb, protoff, th, ...)\nskb_ensure_writable(skb, optend)\npskb_expand_head()        /* kfree(old skb->head) */\n...\ninet_proto_csum_replace4(&th->check, ...)\n/* writes into freed head, or\ninto the caller's stack copy\nleaving the on-wire checksum\nstale */\nThe option bytes are written through skb->data 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.\nFix by re-deriving th from skb->data + protoff immediately after\nskb_ensure_writable() succeeds, so the subsequent checksum update\ntargets the linear, writable header.", "A flaw was found in the Linux kernel's netfilter synproxy module. When handling TCP timestamp options, a stale pointer can be used after memory reallocation. This can result in memory corruption, where data is written to a freed memory area, or lead to packets being sent with an incorrect checksum. A remote attacker could potentially exploit this to cause system instability or network communication issues." ],
  "affected_release" : [ {
    "product_name" : "Red Hat Enterprise Linux 8",
    "release_date" : "2026-09-08T00:00:00Z",
    "advisory" : "RHSA-2026:64770",
    "cpe" : "cpe:/a:redhat:enterprise_linux:8::nfv",
    "package" : "kernel-rt-0:4.18.0-553.160.1.rt7.501.el8_10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "release_date" : "2026-08-20T00:00:00Z",
    "advisory" : "RHSA-2026:57252",
    "cpe" : "cpe:/a:redhat:enterprise_linux:9",
    "package" : "kernel-0:5.14.0-687.41.1.el9_8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "release_date" : "2026-08-20T00:00:00Z",
    "advisory" : "RHSA-2026:57252",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9",
    "package" : "kernel-0:5.14.0-687.41.1.el9_8"
  } ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "erlang27",
    "cpe" : "cpe:/a:redhat:hummingbird:1",
    "impact" : "important"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-64007\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-64007\nhttps://lore.kernel.org/linux-cve-announce/2026071908-CVE-2026-64007-5e61@gregkh/T" ],
  "name" : "CVE-2026-64007",
  "csaw" : false
}