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net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd() In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points directly into the mmap'd TX ring buffer shared with userspace. The kernel validates the header via __packet_snd_vnet_parse() but then re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent userspace thread can modify the vnet_hdr fields between validation and use, bypassing all safety checks. The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr to a stack-local variable. All other vnet_hdr consumers in the kernel (tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX path is the only caller of virtio_net_hdr_to_skb() that reads directly from user-controlled shared memory. Fix this by copying vnet_hdr from the mmap'd ring buffer to a stack-local variable before validation and use, consistent with the approach used in packet_snd() and all other callers.

Announced Source revision 1
Original source ↗

CVE-2026-31700

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-31700

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "1d036d25e5609ba73fee6a88db01c306b140d512",
        "lessThan": "0f4c9754956b86de158a4af5278c5cf5bda9439e",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1d036d25e5609ba73fee6a88db01c306b140d512",
        "lessThan": "714aa973da8163925eda7efd49361ccbee21ee46",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1d036d25e5609ba73fee6a88db01c306b140d512",
        "lessThan": "1490f82353bdabc09265a74e645b07f05cf4188e",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1d036d25e5609ba73fee6a88db01c306b140d512",
        "lessThan": "74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1d036d25e5609ba73fee6a88db01c306b140d512",
        "lessThan": "3a1bf9116ea31470b89692585c3910dfe830dcdd",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1d036d25e5609ba73fee6a88db01c306b140d512",
        "lessThan": "28324a3b62d9ce7f9bdd65a8ce63f382041d1b27",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1d036d25e5609ba73fee6a88db01c306b140d512",
        "lessThan": "48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1d036d25e5609ba73fee6a88db01c306b140d512",
        "lessThan": "2c054e17d9d41f1020376806c7f750834ced4dc5",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/packet/af_packet.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "4.6"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "4.6",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.259",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.210",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.176",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.136",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.84",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.25",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.0.2",
        "versionType": "semver",
        "lessThanOrEqual": "7.0.*"
      },
      {
        "status": "unaffected",
        "version": "7.1",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/packet/af_packet.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-31700

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#39985 · Revision 1
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Publisher date
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