CVE-2026-90078

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_skbmod: fix length calculations and avoid invalid header warnings syzbot reported a warning in skb_network_header_len() triggered by tcf_skbmod_act(): !skb_transport_header_was_set(skb) WARNING: CPU: 0 PID: 14949 at include/linux/skbuff.h:3243 skb_network_header_len include/linux/skbuff.h:3243 [inline] WARNING: CPU: 0 PID: 14949 at net/sched/act_skbmod.c:55 tcf_skbmod_act+0xfe8/0x1810 net/sched/act_skbmod.c:55 There are a few issues in tcf_skbmod_act(): 1. Calling skb_network_header_len() assumes skb->transport_header is set, which is not guaranteed when tcf_skbmod_act() runs at TC ingress. 2. Unconditionally calling skb_mac_header_len() at the beginning of tcf_skbmod_act() triggers a warning on L3 devices (e.g. TUN) where the MAC header is unset, evaluating to an underflowed garbage length. 3. On TC ingress, skb->data points to the network header. Adding the MAC header length to the IP header length causes skb_ensure_writable() to request more bytes than the actual IP packet length, dropping valid short packets (e.g. 28-byte UDP/IPv4 packets). Fix these by: - Using skb_network_offset(skb) + sizeof(struct iphdr/ipv6hdr) for SKBMOD_F_ECN so that the required length is correctly calculated on both ingress (offset == 0) and egress (offset == mac_len). - Setting max_edit_len to ETH_HLEN for Ethernet header modifications after validating ARPHRD_ETHER.

Severity

Not scored

CVSS score

Not available

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-17 17:16:57.057000

Last modified

2026-10-19 09:18:56.630000

View original CVE JSON

{
  "id": "CVE-2026-90078",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-17T17:16:57.057",
  "lastModified": "2026-10-19T09:18:56.630",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "net/sched/act_skbmod.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "56af5e749f20c3a540310c207dcc373f4f09156e",
              "lessThan": "985a37781ade19061400100c2ba0f43979dd4d63",
              "versionType": "git",
              "status": "affected"
            },
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              "lessThan": "d896843d8d925f0adbba319020595cfb1a7bcd57",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "56af5e749f20c3a540310c207dcc373f4f09156e",
              "lessThan": "0675cff3c2924eb9b80d9dd250cf56a1140af157",
              "versionType": "git",
              "status": "affected"
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            {
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              "versionType": "git",
              "status": "affected"
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              "versionType": "git",
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              "versionType": "git",
              "status": "affected"
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            {
              "version": "56af5e749f20c3a540310c207dcc373f4f09156e",
              "lessThan": "81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "net/sched/act_skbmod.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "5.15",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "5.15",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.15.221",
              "lessThanOrEqual": "5.15.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.188",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.157",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.110",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.52",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.6",
              "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/0675cff3c2924eb9b80d9dd250cf56a1140af157",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
      "url": "https://git.kernel.org/stable/c/e8a2027b7e686784a69b2dfcee841d779919f313",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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}