{"id":"CVE-2026-74310","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-74310","summary":"vhost/net: complete zerocopy ubufs only once","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nvhost/net: complete zerocopy ubufs only once\n\nvhost-net initializes one ubuf_info per outstanding zerocopy TX\ndescriptor and hands it to the backend socket.  The networking stack may\nthen clone a zerocopy skb before all skb references are released.  For\nexample, batman-adv fragmentation reaches skb_split(), which calls\nskb_zerocopy_clone() and increments the same ubuf_info refcount.\n\nvhost_zerocopy_complete() currently treats every ubuf callback as a\ncompleted vhost descriptor.  It dereferences ubuf->ctx, writes the\ndescriptor completion state, and drops the vhost_net_ubuf_ref even when\nthe callback only releases a cloned skb reference.  A backend reset can\ntherefore wait for and free the vhost_net_ubuf_ref while another cloned\nskb still carries the same ubuf_info.  A later completion then\ndereferences the freed ubufs pointer.\n\nKASAN reports the stale completion as:\n\n  BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x1d7/0x1f0\n  BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x101/0x1f0\n  vhost_zerocopy_complete\n  skb_copy_ubufs\n  __dev_forward_skb2\n  veth_xmit\n\nThe freed object was allocated from vhost_net_ioctl() while setting the\nbackend and freed through kfree_rcu()/kvfree_rcu_bulk after backend\nremoval, while delayed skb completion still reached\nvhost_zerocopy_complete().\n\nHonor the generic ubuf_info refcount before touching vhost state, and run\nthe vhost descriptor completion only for the final ubuf reference.  This\nmatches the msg_zerocopy_complete() ownership rule for cloned zerocopy\nskbs.","published":"2026-08-15T05:58:10.043Z","modified":"2026-08-18T03:56:46.171368479Z","cvss":{"score":9.3,"severity":"CRITICAL","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.1.178"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/321c73baf54d971ce3771fea275c98a247f7ee35"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6445b945024f4c7675ae5352b2d5885cb1deea71"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8f6898fe80794f2d7c3d38c1158c806e4074a1c4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a9f8a1d2e3ff511eafd4c5462481950c2f4d2b5d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c069437924663539a93a1e5afe90838d9ccee284"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ea71f873423fb73e66ad88936d6759ac0ad4aa53"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74310.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74310"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-18T03:56:46.171368479Z"}}