Vulnerability-Lookup

GHSA-23Q4-679M-QGXW

Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-25 06:31

Details

In the Linux kernel, the following vulnerability has been resolved:

net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp()

The commit 4f61f133f354 ("net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null") fixed a crash in tap_get_user() by assigning skb->dev before calling tun_vnet_hdr_to_skb(). This is required because virtio_net_hdr_to_skb() may invoke dev_parse_header_protocol(), which dereferences skb->dev. Without the assignment, a NULL pointer dereference can occur.

However, tap_get_user_xdp() still parses the virtio-net header before assigning skb->dev. When the vhost TX path passes an XDP buffer containing a GSO virtio-net header but the protocol is set to zero on purpose, tun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb->dev is still NULL, resulting in a crash.

Fix this by looking up the tap device and assigning skb->dev before calling tun_vnet_hdr_to_skb(), matching the ordering already used in tap_get_user(). Preserve the existing RCU read-side critical section across dev_queue_xmit().

Severity

7.1 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74684"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-22T16:16:42Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: tap: set skb-\u003edev before parsing virtio net header in tap_get_user_xdp()\n\nThe commit 4f61f133f354 (\"net: tap: NULL pointer derefence in\ndev_parse_header_protocol when skb-\u003edev is null\") fixed a crash in\ntap_get_user() by assigning skb-\u003edev before calling tun_vnet_hdr_to_skb().\nThis is required because virtio_net_hdr_to_skb() may invoke\ndev_parse_header_protocol(), which dereferences skb-\u003edev. Without the\nassignment, a NULL pointer dereference can occur.\n\nHowever, tap_get_user_xdp() still parses the virtio-net header before\nassigning skb-\u003edev. When the vhost TX path passes an XDP buffer containing\na GSO virtio-net header but the protocol is set to zero on purpose,\ntun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb-\u003edev\nis still NULL, resulting in a crash.\n\nFix this by looking up the tap device and assigning skb-\u003edev before calling\ntun_vnet_hdr_to_skb(), matching the ordering already used in\ntap_get_user(). Preserve the existing RCU read-side critical section across\ndev_queue_xmit().",
  "id": "GHSA-23q4-679m-qgxw",
  "modified": "2026-08-25T06:31:27Z",
  "published": "2026-08-22T18:30:29Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74684"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/15583b07fd691a844fbf7b3ad612cdc9e9a657c0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3874892dd27d5387aa9a06f58d9060f18f351d24"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8b444b126cd8e4473e652f529753ed4dd1360a9c"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-74684 (GCVE-0-2026-74684)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-25 05:41

Title

net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp()

Summary

In the Linux kernel, the following vulnerability has been resolved: net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp() The commit 4f61f133f354 ("net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null") fixed a crash in tap_get_user() by assigning skb->dev before calling tun_vnet_hdr_to_skb(). This is required because virtio_net_hdr_to_skb() may invoke dev_parse_header_protocol(), which dereferences skb->dev. Without the assignment, a NULL pointer dereference can occur. However, tap_get_user_xdp() still parses the virtio-net header before assigning skb->dev. When the vhost TX path passes an XDP buffer containing a GSO virtio-net header but the protocol is set to zero on purpose, tun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb->dev is still NULL, resulting in a crash. Fix this by looking up the tap device and assigning skb->dev before calling tun_vnet_hdr_to_skb(), matching the ordering already used in tap_get_user(). Preserve the existing RCU read-side critical section across dev_queue_xmit().

Severity

7.1 (High)


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

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/15583b07fd691a844…
https://git.kernel.org/stable/c/8b444b126cd8e4473…
https://git.kernel.org/stable/c/164c31ee252ebd1ac…
https://git.kernel.org/stable/c/3874892dd27d5387a…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 924a9bc362a5223cd448ca08c3dde21235adc310 , < 15583b07fd691a844fbf7b3ad612cdc9e9a657c0 (git) Affected: 924a9bc362a5223cd448ca08c3dde21235adc310 , < 8b444b126cd8e4473e652f529753ed4dd1360a9c (git) Affected: 924a9bc362a5223cd448ca08c3dde21235adc310 , < 164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b (git) Affected: 924a9bc362a5223cd448ca08c3dde21235adc310 , < 3874892dd27d5387aa9a06f58d9060f18f351d24 (git) Affected: ea3fb2ce5fa794d02135f5c079e05cd6fc3f545d (git) Affected: 54ef8243c3c8e90f1ea5792e6752e021a25c8eb3 (git) Affected: ca278267d6cd9544645731732455b6b20cb0e895 (git) Affected: faa3baa2828c5e1c4374f3e60041f75c64f5fcb6 (git) Affected: 99b1d3f74b9ef72c2f74c8e4c078e1bc0706e748 (git) Affected: 4.14.226 , < 4.15 (semver) Affected: 4.19.181 , < 4.20 (semver) Affected: 5.4.106 , < 5.5 (semver) Affected: 5.10.24 , < 5.11 (semver) Affected: 5.11.7 , < 5.12 (semver)
Linux	Linux	Affected: 5.12 Unaffected: 0 , < 5.12 (semver) Unaffected: 6.12.105 , ≤ 6.12.* (semver) Unaffected: 6.18.45 , ≤ 6.18.* (semver) Unaffected: 7.1.9 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/tap.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "15583b07fd691a844fbf7b3ad612cdc9e9a657c0",
              "status": "affected",
              "version": "924a9bc362a5223cd448ca08c3dde21235adc310",
              "versionType": "git"
            },
            {
              "lessThan": "8b444b126cd8e4473e652f529753ed4dd1360a9c",
              "status": "affected",
              "version": "924a9bc362a5223cd448ca08c3dde21235adc310",
              "versionType": "git"
            },
            {
              "lessThan": "164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b",
              "status": "affected",
              "version": "924a9bc362a5223cd448ca08c3dde21235adc310",
              "versionType": "git"
            },
            {
              "lessThan": "3874892dd27d5387aa9a06f58d9060f18f351d24",
              "status": "affected",
              "version": "924a9bc362a5223cd448ca08c3dde21235adc310",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ea3fb2ce5fa794d02135f5c079e05cd6fc3f545d",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "54ef8243c3c8e90f1ea5792e6752e021a25c8eb3",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ca278267d6cd9544645731732455b6b20cb0e895",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "faa3baa2828c5e1c4374f3e60041f75c64f5fcb6",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "99b1d3f74b9ef72c2f74c8e4c078e1bc0706e748",
              "versionType": "git"
            },
            {
              "lessThan": "4.15",
              "status": "affected",
              "version": "4.14.226",
              "versionType": "semver"
            },
            {
              "lessThan": "4.20",
              "status": "affected",
              "version": "4.19.181",
              "versionType": "semver"
            },
            {
              "lessThan": "5.5",
              "status": "affected",
              "version": "5.4.106",
              "versionType": "semver"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.24",
              "versionType": "semver"
            },
            {
              "lessThan": "5.12",
              "status": "affected",
              "version": "5.11.7",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/tap.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.12"
            },
            {
              "lessThan": "5.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.105",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.105",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.45",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.9",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "5.12",
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                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "4.14.226",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "4.19.181",
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                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.4.106",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.10.24",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.11.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: tap: set skb-\u003edev before parsing virtio net header in tap_get_user_xdp()\n\nThe commit 4f61f133f354 (\"net: tap: NULL pointer derefence in\ndev_parse_header_protocol when skb-\u003edev is null\") fixed a crash in\ntap_get_user() by assigning skb-\u003edev before calling tun_vnet_hdr_to_skb().\nThis is required because virtio_net_hdr_to_skb() may invoke\ndev_parse_header_protocol(), which dereferences skb-\u003edev. Without the\nassignment, a NULL pointer dereference can occur.\n\nHowever, tap_get_user_xdp() still parses the virtio-net header before\nassigning skb-\u003edev. When the vhost TX path passes an XDP buffer containing\na GSO virtio-net header but the protocol is set to zero on purpose,\ntun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb-\u003edev\nis still NULL, resulting in a crash.\n\nFix this by looking up the tap device and assigning skb-\u003edev before calling\ntun_vnet_hdr_to_skb(), matching the ordering already used in\ntap_get_user(). Preserve the existing RCU read-side critical section across\ndev_queue_xmit()."
        }
      ],
      "metrics": [
        {
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            "baseSeverity": "HIGH",
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            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - A malicious KVM guest reaches tap_get_user_xdp() by kicking the virtio-net TX virtqueue; vhost_net handle_tx_copy batches XDP buffers and invokes tap_sendmsg(TUN_MSG_PTR), not via any host network packet-receive path.\nAC:L - On typical QEMU/KVM vhost-net+tap/macvtap backends with TX batching enabled, a guest fully controls virtio-net GSO headers and Ethernet frames; sending GSO with ethertype 0 deterministically hits dev_parse_header_protocol() with skb-\u003edev NULL without races.\nPR:N - No host root or capabilities are required; a malicious cloud VM tenant only needs code execution inside a guest using virtio-net with a vhost-net tap backend, matching other guest-to-host virtio/KVM CNA scores.\nUI:N - No separate victim action is needed; the attacker submits crafted virtio-net TX descriptors from their own guest workload during normal VM operation without requiring host administrator interaction.\nS:C - Guest-supplied virtio-net TX data triggers a NULL pointer dereference in host tap_get_user_xdp(), panicking the physical host kernel and crossing the KVM guest-to-host virtualization security boundary.\nC:N - The failure mode is a NULL pointer dereference at dev-\u003eheader_ops with skb-\u003edev unset; there is no demonstrated out-of-bounds read, use-after-free, or other memory corruption that could disclose host kernel data.\nI:N - No guest-controlled host memory write or control-flow hijack occurs; the host kernel oopses on the NULL dereference before any exploitable modification beyond the immediate crash.\nA:H - The NULL pointer dereference in dev_parse_header_protocol() provokes a host kernel oops/panic in the vhost worker during guest virtio-net TX, denying availability of the hypervisor and all co-resident VMs."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-25T05:41:30.283Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/15583b07fd691a844fbf7b3ad612cdc9e9a657c0"
        },
        {
          "url": "https://git.kernel.org/stable/c/8b444b126cd8e4473e652f529753ed4dd1360a9c"
        },
        {
          "url": "https://git.kernel.org/stable/c/164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b"
        },
        {
          "url": "https://git.kernel.org/stable/c/3874892dd27d5387aa9a06f58d9060f18f351d24"
        }
      ],
      "title": "net: tap: set skb-\u003edev before parsing virtio net header in tap_get_user_xdp()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74684",
    "datePublished": "2026-08-22T15:32:50.846Z",
    "dateReserved": "2026-08-15T05:44:03.926Z",
    "dateUpdated": "2026-08-25T05:41:30.283Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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