{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-90078",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2026-90078"
  ],
  "published": "2026-09-17T16:10:40Z",
  "summary": "net/sched: act_skbmod: fix length calculations and avoid invalid header warnings",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_skbmod: fix length calculations and avoid invalid header warnings\n\nsyzbot reported a warning in skb_network_header_len() triggered\nby tcf_skbmod_act():\n\n  !skb_transport_header_was_set(skb)\n  WARNING: CPU: 0 PID: 14949 at include/linux/skbuff.h:3243 skb_network_header_len include/linux/skbuff.h:3243 [inline]\n  WARNING: CPU: 0 PID: 14949 at net/sched/act_skbmod.c:55 tcf_skbmod_act+0xfe8/0x1810 net/sched/act_skbmod.c:55\n\nThere are a few issues in tcf_skbmod_act():\n\n1. Calling skb_network_header_len() assumes skb->transport_header is set,\n   which is not guaranteed when tcf_skbmod_act() runs at TC ingress.\n2. Unconditionally calling skb_mac_header_len() at the beginning of\n   tcf_skbmod_act() triggers a warning on L3 devices (e.g. TUN) where the\n   MAC header is unset, evaluating to an underflowed garbage length.\n3. On TC ingress, skb->data points to the network header. Adding the MAC\n   header length to the IP header length causes skb_ensure_writable() to\n   request more bytes than the actual IP packet length, dropping valid\n   short packets (e.g. 28-byte UDP/IPv4 packets).\n\nFix these by:\n- Using skb_network_offset(skb) + sizeof(struct iphdr/ipv6hdr) for\n  SKBMOD_F_ECN so that the required length is correctly calculated on\n  both ingress (offset == 0) and egress (offset == mac_len).\n- Setting max_edit_len to ETH_HLEN for Ethernet header modifications\n  after validating ARPHRD_ETHER.",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.188",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-90078"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/985a37781ade19061400100c2ba0f43979dd4d63"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/d896843d8d925f0adbba319020595cfb1a7bcd57"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/0675cff3c2924eb9b80d9dd250cf56a1140af157"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e8a2027b7e686784a69b2dfcee841d779919f313"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/1719865b20b22c88d2a55e922eff5ca31b0841f6"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/62126464f3a6159c0a3dd89e196ba65bfeb0afc6"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-09-17T16:10:40Z"
  }
}