CVE-2026-52940 (GCVE-0-2026-52940)

Vulnerability from cvelistv5 – Published: 2026-06-24 07:14 – Updated: 2026-06-24 07:14
VLAI
Title
tun: zero the whole vnet header in tun_put_user()
Summary
In the Linux kernel, the following vulnerability has been resolved: tun: zero the whole vnet header in tun_put_user() tun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel without zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb() only initializes the first 10 bytes (sizeof(struct virtio_net_hdr)), leaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack garbage. An unprivileged user can set the vnet header size to 24 with TUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the partially-initialized struct to userspace, leaking 14 bytes of kernel stack on every read of a non-tunnel packet. Fix it the same way tun_get_user() already does by zeroing the whole header right after declaration.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 , < 5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5 (git)
Affected: 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 , < 585cb85e9a29185be05f326369573c2663cf4380 (git)
Affected: 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 , < 7f2fcff15e99bb852f6967396ed12b38376e2c8d (git)
Create a notification for this product.
Linux Linux Affected: 6.17
Unaffected: 0 , < 6.17 (semver)
Unaffected: 6.18.36 , ≤ 6.18.* (semver)
Unaffected: 7.0.13 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/tun.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5",
              "status": "affected",
              "version": "288f30435132d2f9e7a29ec9b9745a4f9dc7fd37",
              "versionType": "git"
            },
            {
              "lessThan": "585cb85e9a29185be05f326369573c2663cf4380",
              "status": "affected",
              "version": "288f30435132d2f9e7a29ec9b9745a4f9dc7fd37",
              "versionType": "git"
            },
            {
              "lessThan": "7f2fcff15e99bb852f6967396ed12b38376e2c8d",
              "status": "affected",
              "version": "288f30435132d2f9e7a29ec9b9745a4f9dc7fd37",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/tun.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.17"
            },
            {
              "lessThan": "6.17",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.36",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.13",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.36",
                  "versionStartIncluding": "6.17",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.13",
                  "versionStartIncluding": "6.17",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "6.17",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntun: zero the whole vnet header in tun_put_user()\n\ntun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel\nwithout zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb()\nonly initializes the first 10 bytes (sizeof(struct virtio_net_hdr)),\nleaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack\ngarbage.\n\nAn unprivileged user can set the vnet header size to 24 with\nTUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the\npartially-initialized struct to userspace, leaking 14 bytes of kernel\nstack on every read of a non-tunnel packet.\n\nFix it the same way tun_get_user() already does by zeroing the whole\nheader right after declaration."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-24T07:14:29.281Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5"
        },
        {
          "url": "https://git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380"
        },
        {
          "url": "https://git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d"
        }
      ],
      "title": "tun: zero the whole vnet header in tun_put_user()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-52940",
    "datePublished": "2026-06-24T07:14:29.281Z",
    "dateReserved": "2026-06-09T07:44:35.370Z",
    "dateUpdated": "2026-06-24T07:14:29.281Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-52940",
      "date": "2026-07-02",
      "epss": "0.00154",
      "percentile": "0.04975"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-52940\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-06-24T08:16:24.287\",\"lastModified\":\"2026-06-24T08:16:24.287\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ntun: zero the whole vnet header in tun_put_user()\\n\\ntun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel\\nwithout zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb()\\nonly initializes the first 10 bytes (sizeof(struct virtio_net_hdr)),\\nleaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack\\ngarbage.\\n\\nAn unprivileged user can set the vnet header size to 24 with\\nTUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the\\npartially-initialized struct to userspace, leaking 14 bytes of kernel\\nstack on every read of a non-tunnel packet.\\n\\nFix it the same way tun_get_user() already does by zeroing the whole\\nheader right after declaration.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"drivers/net/tun.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"288f30435132d2f9e7a29ec9b9745a4f9dc7fd37\",\"lessThan\":\"5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"288f30435132d2f9e7a29ec9b9745a4f9dc7fd37\",\"lessThan\":\"585cb85e9a29185be05f326369573c2663cf4380\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"288f30435132d2f9e7a29ec9b9745a4f9dc7fd37\",\"lessThan\":\"7f2fcff15e99bb852f6967396ed12b38376e2c8d\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"drivers/net/tun.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.17\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.17\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.36\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.13\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.