CVE-2026-63970 (GCVE-0-2026-63970)
Vulnerability from cvelistv5
Published
2026-07-19 14:55
Modified
2026-08-05 12:37
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: vsock/virtio: bind uarg before filling zerocopy skb virtio_transport_send_pkt_info() allocates or reuses the zerocopy uarg before entering the send loop, but virtio_transport_alloc_skb() still fills the skb before it inherits that uarg. When fixed-buffer vectored zerocopy hits MAX_SKB_FRAGS, io_sg_from_iter() may partially attach managed frags and return -EMSGSIZE. The rollback path call kfree_skb() to free an skb that carries SKBFL_MANAGED_FRAG_REFS but no uarg, so skb_release_data() falls through to ordinary frag unref. Pass the uarg into virtio_transport_alloc_skb() and bind it immediately before virtio_transport_fill_skb(). This keeps control or no-payload skbs untouched while ensuring success and rollback share one lifetime rule.
References
Impacted products
Vendor Product Version
Linux Linux Version: 581512a6dc939ef122e49336626ae159f3b8a345
Version: 581512a6dc939ef122e49336626ae159f3b8a345
Version: 581512a6dc939ef122e49336626ae159f3b8a345
Version: 581512a6dc939ef122e49336626ae159f3b8a345
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/vmw_vsock/virtio_transport_common.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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        },
        {
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          "product": "Linux",
          "programFiles": [
            "net/vmw_vsock/virtio_transport_common.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.7"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.97",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.97",
                  "versionStartIncluding": "6.7",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "6.18.35",
                  "versionStartIncluding": "6.7",
                  "vulnerable": true
                },
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                  "vulnerable": true
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "6.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvsock/virtio: bind uarg before filling zerocopy skb\n\nvirtio_transport_send_pkt_info() allocates or reuses the zerocopy uarg\nbefore entering the send loop, but virtio_transport_alloc_skb() still\nfills the skb before it inherits that uarg. When fixed-buffer vectored\nzerocopy hits MAX_SKB_FRAGS, io_sg_from_iter() may partially attach\nmanaged frags and return -EMSGSIZE. The rollback path call kfree_skb()\nto free an skb that carries SKBFL_MANAGED_FRAG_REFS but no uarg, so\nskb_release_data() falls through to ordinary frag unref.\n\nPass the uarg into virtio_transport_alloc_skb() and bind it immediately\nbefore virtio_transport_fill_skb(). This keeps control or no-payload skbs\nuntouched while ensuring success and rollback share one lifetime rule."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached only via local AF_VSOCK transmission (syscall/io_uring send on a connected virtio vsock socket), not by processing remote network packets. Per kernel CVSS guidance, vsock is Local.\nAC:L - An attacker fully controls the trigger: SO_ZEROCOPY, io_uring IORING_OP_SEND_ZC with IORING_RECVSEND_FIXED_BUF and a vectored iov exceeding MAX_SKB_FRAGS (17), causing io_sg_from_iter() to return -EMSGSIZE on a deterministic error rollback path.\nPR:L - Exploitation requires only an unprivileged local process that can open a vsock connection and use io_uring zerocopy send; no CAP_NET_ADMIN or real root is needed beyond ordinary local user access in a virtio-vsock environment (KVM/Firecracker/cloud microVMs).\nUI:N - No victim interaction is required; the attacker triggers the bug directly through their own socket send/io_uring operation.\nS:U - Impact is kernel memory corruption and privilege escalation within the same security domain where the send occurs (guest kernel or host kernel). It is not a cross-boundary VM escape on the receive path; the flaw is in the sender\u0027s local skb teardown.\nC:H - Incorrect __skb_frag_unref() on SKBFL_MANAGED_FRAG_REFS pages without a bound uarg corrupts refcount/lifetime of io_uring registered buffer pages, yielding use-after-free and arbitrary kernel memory read primitives.\nI:H - The refcount corruption is a memory-safety bug in kernel heap/page management that can be leveraged for arbitrary write and control-flow hijacking, not merely a bounded data change.\nA:H - The erroneous frag unref on managed zerocopy pages can cause immediate kernel oops/panic from refcount underflow or use-after-free during skb teardown, independent of full exploitation."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:37:41.706Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/72194f65050958e4c8e069adb6c5d89ef81ca197"
        },
        {
          "url": "https://git.kernel.org/stable/c/b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d"
        },
        {
          "url": "https://git.kernel.org/stable/c/5d317573f1d48e76cce5fb6250452b6e4102e0fb"
        },
        {
          "url": "https://git.kernel.org/stable/c/1e584c304cfb94a759417130b1fc6d30b30c4cce"
        }
      ],
      "title": "vsock/virtio: bind uarg before filling zerocopy skb",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63970",
    "datePublished": "2026-07-19T14:55:57.067Z",
    "dateReserved": "2026-07-19T07:54:57.024Z",
    "dateUpdated": "2026-08-05T12:37:41.706Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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