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)
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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)
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{
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      "affected": [
        {
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          "product": "Linux",
          "programFiles": [
            "drivers/net/tun.c"
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      ],
      "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"
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          "url": "https://git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380"
        },
        {
          "url": "https://git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d"
        }
      ],
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    "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"
  },
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}


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