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CVE-2026-63970 (GCVE-0-2026-63970)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:55 – Updated: 2026-08-05 12:37
VLAI
Title
vsock/virtio: bind uarg before filling zerocopy skb
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.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 581512a6dc939ef122e49336626ae159f3b8a345 , < 72194f65050958e4c8e069adb6c5d89ef81ca197 (git)
Affected: 581512a6dc939ef122e49336626ae159f3b8a345 , < b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d (git)
Affected: 581512a6dc939ef122e49336626ae159f3b8a345 , < 5d317573f1d48e76cce5fb6250452b6e4102e0fb (git)
Affected: 581512a6dc939ef122e49336626ae159f3b8a345 , < 1e584c304cfb94a759417130b1fc6d30b30c4cce (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.7
Unaffected: 0 , < 6.7 (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "product": "Linux",
          "programFiles": [
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          "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."
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              "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."
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    "datePublished": "2026-07-19T14:55:57.067Z",
    "dateReserved": "2026-07-19T07:54:57.024Z",
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      "cve": "CVE-2026-63970",
      "id": "CVE-2026-63970",
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      "cve": "CVE-2026-63970",
      "id": "CVE-2026-63970",
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      "title": "SUSE CVE CVE-2026-63970",
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}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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