CVE-2026-74310
Received Received - Intake

BaseFortify

Publication date: 2026-08-15

Last updated on: 2026-08-15

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: vhost/net: complete zerocopy ubufs only once vhost-net initializes one ubuf_info per outstanding zerocopy TX descriptor and hands it to the backend socket. The networking stack may then clone a zerocopy skb before all skb references are released. For example, batman-adv fragmentation reaches skb_split(), which calls skb_zerocopy_clone() and increments the same ubuf_info refcount. vhost_zerocopy_complete() currently treats every ubuf callback as a completed vhost descriptor. It dereferences ubuf->ctx, writes the descriptor completion state, and drops the vhost_net_ubuf_ref even when the callback only releases a cloned skb reference. A backend reset can therefore wait for and free the vhost_net_ubuf_ref while another cloned skb still carries the same ubuf_info. A later completion then dereferences the freed ubufs pointer. KASAN reports the stale completion as: BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x1d7/0x1f0 BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x101/0x1f0 vhost_zerocopy_complete skb_copy_ubufs __dev_forward_skb2 veth_xmit The freed object was allocated from vhost_net_ioctl() while setting the backend and freed through kfree_rcu()/kvfree_rcu_bulk after backend removal, while delayed skb completion still reached vhost_zerocopy_complete(). Honor the generic ubuf_info refcount before touching vhost state, and run the vhost descriptor completion only for the final ubuf reference. This matches the msg_zerocopy_complete() ownership rule for cloned zerocopy skbs.

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Meta Information

Published
2026-08-15
Last Modified
2026-08-15
Generated
2026-08-15
AI Q&A
2026-08-15
EPSS Evaluated
N/A
NVD
CVE-2026-74310
EUVD
EUVD-2026-59457

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a use-after-free vulnerability in the Linux kernel's vhost-net subsystem. It occurs when zerocopy buffers are improperly handled, leading to a freed memory reference. The issue stems from vhost-net not tracking multiple references to the same zerocopy buffer correctly, causing a backend reset to free resources while cloned skb fragments still reference them.

Detection Guidance

This vulnerability is specific to the Linux kernel's vhost-net subsystem and may not have direct detection commands. Look for KASAN reports indicating slab-use-after-free in vhost_zerocopy_complete or related vhost functions. Check kernel logs for crashes or warnings during high network load with zerocopy TX operations.

Impact Analysis

This vulnerability can cause kernel crashes (oops) due to memory corruption, leading to system instability or denial of service. Attackers might exploit it to crash vulnerable systems or potentially execute arbitrary code with kernel privileges.

Mitigation Strategies

Update the Linux kernel to a patched version that resolves this issue. Disable vhost-net zerocopy features if not required. Monitor kernel logs for related errors and apply vendor security updates promptly.

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