CVE-2026-98954

{
  "id": "CVE-2026-98954",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-10-23T13:17:16.600",
  "lastModified": "2026-10-23T13:17:16.600",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: always dissect GSO packets in __virtio_net_hdr_to_skb()\n\nCommit 9e8db5913264 (\"net: avoid false positives in untrusted gso\nvalidation\") added a '&& skb->network_header' check before flow-dissecting\nGSO packets without VIRTIO_NET_HDR_F_NEEDS_CSUM in\n__virtio_net_hdr_to_skb(), because some callers (such as tun_get_user(),\ntun_xdp_one(), virtnet_receive_done(), and raw_verify_header()) called\nvirtio_net_hdr_*_to_skb() before initializing skb->network_header and\nskb->dev.\n\nBecause __alloc_skb() and __build_skb_around() zero-initialize\nskb->network_header to 0 (unlike mac_header and transport_header which\nare initialized to ~0U), those four callers always had\nskb->network_header == 0 and bypassed flow dissection in\n__virtio_net_hdr_to_skb(). More generally, skb->network_header is an\noffset from skb->head (where 0 is also a valid offset whenever\nskb_headroom(skb) is 0), not a boolean flag.\n\nWhenever the 'if (gso_type && skb->network_header)' branch was skipped,\nthe fallback 'else if (gso_type)' only pulled nh_min_len + thlen (40 bytes\nfor TCPv4) without dissecting the packet, without validating ip_proto or\nn_proto, and without setting skb->transport_header.\n\nIf the packet has a malformed network header, it is not rejected and a\nsubsequent skb_probe_transport_header() also fails, leaving\nskb->transport_header at ~0U (0xffff). Similarly, if an IPv4 packet\ncarries IP options (ihl > 5) or an IPv6 packet carries extension headers,\npulling only nh_min_len + thlen can leave the TCP header outside\nskb->head. In both cases, tcp_hdrlen(skb) in skb_gso_transport_seglen()\nreads out-of-bounds:\n\n  BUG: KASAN: slab-out-of-bounds in skb_gso_transport_seglen\n  Read of size 2 by task poc/133\n  skb_gso_transport_seglen (net/core/gso.c:155)\n  skb_gso_validate_mac_len (net/core/gso.c:270)\n  tbf_enqueue (net/sched/sch_tbf.c:260)\n  dev_qdisc_enqueue (net/core/dev.c:4227)\n  __dev_queue_xmit (net/core/dev.c:4884)\n\nIn addition, checking virtio_net_hdr_match_proto() only inside\n'if (!skb->protocol)' before flow dissection both skipped validation when\nskb->protocol was pre-set by the caller and rejected VLAN-tagged frames\nwhose outer L2 protocol is ETH_P_8021Q or ETH_P_8021AD.\n\nFix this by:\n1. Initializing skb->dev and skb->network_header (plus skb->protocol for\n   IFF_TUN) before virtio_net_hdr_*_to_skb() in tun_get_user(),\n   tun_xdp_one(), virtnet_receive_done(), and raw_verify_header(). In\n   tun_get_user(), drop the redundant skb_reset_mac_header(skb) in the\n   IFF_TUN case since __virtio_net_hdr_to_skb() unconditionally resets\n   mac_header.\n2. Removing '&& skb->network_header' and the unvalidated\n   'else if (gso_type)' fallback in __virtio_net_hdr_to_skb() so all GSO\n   packets without VIRTIO_NET_HDR_F_NEEDS_CSUM are flow-dissected, have\n   their transport header pulled into linear data, and have\n   skb->transport_header set.\n3. Moving the virtio_net_hdr_match_proto() check to after\n   skb_flow_dissect_flow_keys_basic(), validating keys.basic.n_proto\n   against hdr_gso_type."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "arch/um/drivers/vector_transports.c",
            "drivers/net/tun.c",
            "drivers/net/virtio_net.c",
            "include/linux/virtio_net.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "d5be7f632bad0f489879eed0ff4b99bd7fe0b74c",
              "lessThan": "5f4dfdf0077730e9d3ef5b37ceb17a5a56d6f34c",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "d5be7f632bad0f489879eed0ff4b99bd7fe0b74c",
              "lessThan": "44378d02c5aaae24b60a75fbbb539b4aa4db503d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "dac7d4432b13d6b58923c1178b786bcda37c9e9e",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e93384b12443c9bb6830b56b7d299beed432b865",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "f709f7b28d76de327373598a0fda9f916c36b5e6",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "d996573ebd5c528c613e90b7e7daa961d58fa16e",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "c375152be9dd9d6fbf6ae5ac8be337d0590f192a",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "0dab7eb86ea06ce8c530785f1999948c6f223c96",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "ea3fb2ce5fa794d02135f5c079e05cd6fc3f545d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "54ef8243c3c8e90f1ea5792e6752e021a25c8eb3",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "4.14.104",
              "lessThan": "4.15",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "4.19.26",
              "lessThan": "4.20",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "4.20.13",
              "lessThan": "4.21",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "4.14.226",
              "lessThan": "4.15",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "4.19.181",
              "lessThan": "4.20",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "arch/um/drivers/vector_transports.c",
            "drivers/net/tun.c",
            "drivers/net/virtio_net.c",
            "include/linux/virtio_net.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "5.0",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "5.0",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.11",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {},
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/44378d02c5aaae24b60a75fbbb539b4aa4db503d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/5f4dfdf0077730e9d3ef5b37ceb17a5a56d6f34c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}