FKIE_CVE-2026-98377

Vulnerability from fkie_nvd - Published: 2026-10-09 08:16 - Updated: 2026-10-09 08:16
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: vlan: require the MAC header to be present in __vlan_insert_inner_tag() __vlan_insert_inner_tag() only guarantees head room via skb_cow_head(), never that mac_len bytes of MAC header are present. Its ETH_HLEN wrappers - __vlan_insert_tag() under skb_vlan_push(), and vlan_insert_tag() under validate_xmit_vlan() on the generic transmit path - therefore rewrite the first 16 bytes at skb->data: a 12-byte memmove plus two 2-byte stores at +12 and +14. No caller supplies the bound, while the pop helpers use skb_ensure_writable()/pskb_may_pull(). An IFF_TUN device has hard_header_len == 0, so packet_snd() accepts a one-byte AF_PACKET/SOCK_RAW frame. The first vlan push only sets a hwaccel tag; the next - clsact "action vlan push" or bpf_skb_vlan_push() - enters the helper with skb->len still 1. The head comes from skbuff_small_head without __GFP_ZERO, so each push drags bytes from beyond skb->tail into the frame. After three the one-byte send leaves as 13 bytes carrying 11 bytes of uninitialised slab: 0000: 5a b3 62 12 80 88 ff ff 00 b3 62 12 81 `------------------------------' only 0x5a was sent; the rest is slab, here the top 56 bits of a linear-map address Require the MAC header the helper rewrites to be present, so such a frame is dropped rather than transmitted.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/40a5cc4b7251c74f3341332a226d02200e96bccf
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdc
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ab888242fce4f16f6c4d4c6ec53939ad36aa3b3a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f42562dd027dc4ed103fae17b2206e73ea1963c4
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/linux/if_vlan.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "40a5cc4b7251c74f3341332a226d02200e96bccf",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "f42562dd027dc4ed103fae17b2206e73ea1963c4",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdc",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "ab888242fce4f16f6c4d4c6ec53939ad36aa3b3a",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "include/linux/if_vlan.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "lessThan": "2.6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.112",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.55",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvlan: require the MAC header to be present in __vlan_insert_inner_tag()\n\n__vlan_insert_inner_tag() only guarantees head room via skb_cow_head(),\nnever that mac_len bytes of MAC header are present.  Its ETH_HLEN\nwrappers - __vlan_insert_tag() under skb_vlan_push(), and\nvlan_insert_tag() under validate_xmit_vlan() on the generic transmit\npath - therefore rewrite the first 16 bytes at skb-\u003edata: a 12-byte\nmemmove plus two 2-byte stores at +12 and +14.  No caller supplies the\nbound, while the pop helpers use skb_ensure_writable()/pskb_may_pull().\n\nAn IFF_TUN device has hard_header_len == 0, so packet_snd() accepts a\none-byte AF_PACKET/SOCK_RAW frame.  The first vlan push only sets a\nhwaccel tag; the next - clsact \"action vlan push\" or\nbpf_skb_vlan_push() - enters the helper with skb-\u003elen still 1.  The\nhead comes from skbuff_small_head without __GFP_ZERO, so each push\ndrags bytes from beyond skb-\u003etail into the frame.  After three the\none-byte send leaves as 13 bytes carrying 11 bytes of uninitialised\nslab:\n\n  0000: 5a b3 62 12 80 88 ff ff 00 b3 62 12 81\n           `------------------------------\u0027\n  only 0x5a was sent; the rest is slab, here the top 56 bits of a\n  linear-map address\n\nRequire the MAC header the helper rewrites to be present, so such a\nframe is dropped rather than transmitted."
    }
  ],
  "id": "CVE-2026-98377",
  "lastModified": "2026-10-09T08:16:56.010",
  "metrics": {},
  "published": "2026-10-09T08:16:56.010",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/40a5cc4b7251c74f3341332a226d02200e96bccf"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdc"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ab888242fce4f16f6c4d4c6ec53939ad36aa3b3a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f42562dd027dc4ed103fae17b2206e73ea1963c4"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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