Vulnerability-Lookup

FKIE_CVE-2026-31700

Vulnerability from fkie_nvd - Published: 2026-05-01 14:16 - Updated: 2026-05-06 19:01

Severity ?

7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Summary

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.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/28324a3b62d9ce7f9bdd65a8ce63f382041d1b27	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/2c054e17d9d41f1020376806c7f750834ced4dc5	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3a1bf9116ea31470b89692585c3910dfe830dcdd	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121	Patch

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	7.1
linux	linux_kernel	7.1

JSON

To clipboard

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "7A6CE177-C7BA-4E34-9D61-035565B5FFF5",
              "versionEndExcluding": "6.6.136",
              "versionStartIncluding": "4.6",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "D4ECA0DE-AFF5-4688-B219-4CA2336CA5B7",
              "versionEndExcluding": "6.12.84",
              "versionStartIncluding": "6.7",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "8B0A7E0E-F6D8-45DB-8CD9-01839FE40A6C",
              "versionEndExcluding": "6.18.25",
              "versionStartIncluding": "6.13",
              "vulnerable": true
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            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "1BD58F1E-7C20-4C0D-92A2-FAC5CBFBE8A8",
              "versionEndExcluding": "7.0.2",
              "versionStartIncluding": "6.19",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*",
              "matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*",
              "matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: fix TOCTOU race on mmap\u0027d vnet_hdr in tpacket_snd()\n\nIn tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points\ndirectly into the mmap\u0027d TX ring buffer shared with userspace. The\nkernel validates the header via __packet_snd_vnet_parse() but then\nre-reads all fields later in virtio_net_hdr_to_skb(). A concurrent\nuserspace thread can modify the vnet_hdr fields between validation\nand use, bypassing all safety checks.\n\nThe non-TPACKET path (packet_snd()) already correctly copies vnet_hdr\nto a stack-local variable. All other vnet_hdr consumers in the kernel\n(tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX\npath is the only caller of virtio_net_hdr_to_skb() that reads directly\nfrom user-controlled shared memory.\n\nFix this by copying vnet_hdr from the mmap\u0027d ring buffer to a\nstack-local variable before validation and use, consistent with the\napproach used in packet_snd() and all other callers."
    }
  ],
  "id": "CVE-2026-31700",
  "lastModified": "2026-05-06T19:01:07.423",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-05-01T14:16:19.907",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/28324a3b62d9ce7f9bdd65a8ce63f382041d1b27"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/2c054e17d9d41f1020376806c7f750834ced4dc5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/3a1bf9116ea31470b89692585c3910dfe830dcdd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-362"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}

CVE-2026-31700 (GCVE-0-2026-31700)

Vulnerability from cvelistv5 – Published: 2026-05-01 13:56 – Updated: 2026-05-03 05:45

Title

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

Summary

Severity ?

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux

References

URL

Tags

	https://git.kernel.org/stable/c/74e2db36fe50e3ad9…
	https://git.kernel.org/stable/c/3a1bf9116ea31470b…
	https://git.kernel.org/stable/c/28324a3b62d9ce7f9…
	https://git.kernel.org/stable/c/48a6ef291a17639e1…
	https://git.kernel.org/stable/c/2c054e17d9d41f102…

Impacted products

Vendor

Product

Version

Linux

Affected: 1d036d25e5609ba73fee6a88db01c306b140d512 , < 74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121 (git)
Affected: 1d036d25e5609ba73fee6a88db01c306b140d512 , < 3a1bf9116ea31470b89692585c3910dfe830dcdd (git)
Affected: 1d036d25e5609ba73fee6a88db01c306b140d512 , < 28324a3b62d9ce7f9bdd65a8ce63f382041d1b27 (git)
Affected: 1d036d25e5609ba73fee6a88db01c306b140d512 , < 48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b (git)
Affected: 1d036d25e5609ba73fee6a88db01c306b140d512 , < 2c054e17d9d41f1020376806c7f750834ced4dc5 (git)

Linux

Affected: 4.6
Unaffected: 0 , < 4.6 (semver)
Unaffected: 6.6.136 , ≤ 6.6.* (semver)
Unaffected: 6.12.84 , ≤ 6.12.* (semver)
Unaffected: 6.18.25 , ≤ 6.18.* (semver)
Unaffected: 7.0.2 , ≤ 7.0.* (semver)
Unaffected: 7.1-rc1 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/packet/af_packet.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "versionType": "git"
            }
          ]
        },
        {
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          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.6"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "6.6.136",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.12.84",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.18.25",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.0.2",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1-rc1",
              "versionType": "original_commit_for_fix"
            }
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        }
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      "cpeApplicability": [
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              "cpeMatch": [
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        }
      ],
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            "version": "3.1"
          }
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        "dateUpdated": "2026-05-03T05:45:25.979Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
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        },
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        },
        {
          "url": "https://git.kernel.org/stable/c/2c054e17d9d41f1020376806c7f750834ced4dc5"
        }
      ],
      "title": "net/packet: fix TOCTOU race on mmap\u0027d vnet_hdr in tpacket_snd()",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31700",
    "datePublished": "2026-05-01T13:56:00.205Z",
    "dateReserved": "2026-03-09T15:48:24.132Z",
    "dateUpdated": "2026-05-03T05:45:25.979Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

FKIE_CVE-2026-31700

CVE-2026-31700 (GCVE-0-2026-31700)

Tags

Sightings

Nomenclature