CVE-2026-64114 (GCVE-0-2026-64114)
Vulnerability from cvelistv5
Published
2026-07-19 15:40
Modified
2026-08-05 12:39
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv4: raw: reject IP_HDRINCL packets with ihl < 5 raw_send_hdrinc() validates that the caller-supplied IPv4 header fits within the message length: iphlen = iph->ihl * 4; err = -EINVAL; if (iphlen > length) goto error_free; if (iphlen >= sizeof(*iph)) { /* fix up saddr, tot_len, id, csum, transport_header */ } It does not, however, reject ihl < 5. For such a packet the "if (iphlen >= sizeof(*iph))" branch is skipped, leaving the crafted iphdr untouched, but the packet is still handed to __ip_local_out() and onward. Downstream consumers that read iph->ihl assume a sane value: net/ipv4/ah4.c:ah_output() in particular subtracts sizeof(struct iphdr) from top_iph->ihl * 4 and passes the (signed-int-negative, then cast to size_t) result to memcpy(), producing an OOB access of length close to SIZE_MAX and a host kernel panic. An IPv4 header with ihl < 5 is malformed by definition (RFC 791: "Internet Header Length is the length of the internet header in 32 bit words ... Note that the minimum value for a correct header is 5."). The kernel should not be willing to inject such a packet into its own output path. Reject "iphlen < sizeof(*iph)" alongside the existing "iphlen > length" check. This matches the principle that locally constructed packets that re-enter the IP stack must pass the same basic sanity tests that a foreign packet would be subjected to. Once this lands, the "if (iphlen >= sizeof(*iph))" wrapper around the fixup branch becomes redundant; left in place to keep the patch minimal and backport-friendly. A follow-up can unwrap it. Note that commit 86f4c90a1c5c ("ipv4, ipv6: ensure raw socket message is big enough to hold an IP header") ensures the message buffer is large enough to hold an iphdr, but does not constrain the self-reported iph->ihl. Reachability: the malformed packet source is any caller with CAP_NET_RAW, including an unprivileged process in a user+net namespace on a kernel with CONFIG_USER_NS=y. The reproduced AH crash also requires a matching xfrm AH policy on the outgoing route; a container granted CAP_NET_ADMIN can install that state and policy in its netns. Loopback bypasses xfrm_output, so the trigger uses a real netdev. Reproduced on UML + KASAN: kernel-mode fault at addr 0x0 with memcpy_orig at the crash site. Same shape reproduces inside a rootless Docker container with --cap-add NET_ADMIN on a stock distro kernel.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/raw.c"
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
        {
          "nodes": [
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                  "vulnerable": true
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: raw: reject IP_HDRINCL packets with ihl \u003c 5\n\nraw_send_hdrinc() validates that the caller-supplied IPv4 header\nfits within the message length:\n\n    iphlen = iph-\u003eihl * 4;\n    err = -EINVAL;\n    if (iphlen \u003e length)\n        goto error_free;\n\n    if (iphlen \u003e= sizeof(*iph)) {\n        /* fix up saddr, tot_len, id, csum, transport_header */\n    }\n\nIt does not, however, reject ihl \u003c 5.  For such a packet the\n\"if (iphlen \u003e= sizeof(*iph))\" branch is skipped, leaving the\ncrafted iphdr untouched, but the packet is still handed to\n__ip_local_out() and onward.  Downstream consumers that read\niph-\u003eihl assume a sane value: net/ipv4/ah4.c:ah_output() in\nparticular subtracts sizeof(struct iphdr) from top_iph-\u003eihl * 4\nand passes the (signed-int-negative, then cast to size_t)\nresult to memcpy(), producing an OOB access of length close to\nSIZE_MAX and a host kernel panic.\n\nAn IPv4 header with ihl \u003c 5 is malformed by definition (RFC 791:\n\"Internet Header Length is the length of the internet header in\n32 bit words ... Note that the minimum value for a correct header\nis 5.\").  The kernel should not be willing to inject such a\npacket into its own output path.\n\nReject \"iphlen \u003c sizeof(*iph)\" alongside the existing\n\"iphlen \u003e length\" check.  This matches the principle that locally\nconstructed packets that re-enter the IP stack must pass the same\nbasic sanity tests that a foreign packet would be subjected to.\n\nOnce this lands, the \"if (iphlen \u003e= sizeof(*iph))\" wrapper around\nthe fixup branch becomes redundant; left in place to keep the\npatch minimal and backport-friendly.  A follow-up can unwrap it.\n\nNote that commit 86f4c90a1c5c (\"ipv4, ipv6: ensure raw socket\nmessage is big enough to hold an IP header\") ensures the message\nbuffer is large enough to hold an iphdr, but does not constrain\nthe self-reported iph-\u003eihl.\n\nReachability: the malformed packet source is any caller with\nCAP_NET_RAW, including an unprivileged process in a user+net\nnamespace on a kernel with CONFIG_USER_NS=y.  The reproduced AH\ncrash also requires a matching xfrm AH policy on the outgoing\nroute; a container granted CAP_NET_ADMIN can install that state\nand policy in its netns.  Loopback bypasses xfrm_output, so the\ntrigger uses a real netdev.\n\nReproduced on UML + KASAN: kernel-mode fault at addr 0x0 with\nmemcpy_orig at the crash site.  Same shape reproduces inside a\nrootless Docker container with --cap-add NET_ADMIN on a stock\ndistro kernel."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires local syscalls (socket/sendmsg on a raw IP_HDRINCL socket); malformed packets are injected locally into the output path, not via remote network ingress which validates ihl \u003e= 5.\nAC:L - The attacker fully controls the crafted header ihl value and can install the required xfrm AH policy and route via CAP_NET_ADMIN in their own network namespace, making exploitation reliable without conditions outside attacker control.\nPR:L - Triggering requires CAP_NET_RAW for raw sockets and CAP_NET_ADMIN to install xfrm AH policy, both obtainable by an unprivileged user via user+network namespaces or a container granted NET_ADMIN without init-namespace root.\nUI:N - No victim interaction is required; the attacker sends the malformed packet directly through their own raw socket and configured IPsec policy.\nS:U - Impact is kernel memory corruption and panic within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.\nC:H - The integer underflow in ah_output() memcpy length produces an out-of-bounds read of near SIZE_MAX bytes, providing an arbitrary kernel memory read primitive beyond any bounded disclosure.\nI:H - The same memcpy with underflowed length causes a massive out-of-bounds write that can corrupt adjacent kernel heap memory and be leveraged for control-flow hijacking.\nA:H - The OOB memcpy reliably causes a kernel-mode fault and host panic, as reproduced with KASAN and in a rootless Docker container, denying all system availability."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:39:23.263Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1065b9efa4126df559b03a849c139ecfae92cd25"
        },
        {
          "url": "https://git.kernel.org/stable/c/bc20dbd48c26e743f7e0845020c11ed2ce8b15ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/5a564f737ec54d63e8ee221d3ff396d07586d464"
        },
        {
          "url": "https://git.kernel.org/stable/c/3c5411fa4944ed99af3d9d1de750ea8169b6dac9"
        },
        {
          "url": "https://git.kernel.org/stable/c/145e9afa5b905229b4788bb72c3255f5a5f77508"
        },
        {
          "url": "https://git.kernel.org/stable/c/7725cd3b471740fd23d25ed1da722c671fb2a5d3"
        },
        {
          "url": "https://git.kernel.org/stable/c/bbe0be67de296176e7243c76e3d9f02f6ae9ff0b"
        },
        {
          "url": "https://git.kernel.org/stable/c/915fab69823a14c170dbaa3b41978768e0fe62fc"
        }
      ],
      "title": "ipv4: raw: reject IP_HDRINCL packets with ihl \u003c 5",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64114",
    "datePublished": "2026-07-19T15:40:14.854Z",
    "dateReserved": "2026-07-19T07:54:57.035Z",
    "dateUpdated": "2026-08-05T12:39:23.263Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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