CVE-2026-74356

Status: UPDATED  |  Advisory ID: CVE-2026-74356

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

vhost: fix vhost_get_avail_idx for a non empty ring

vhost_get_avail_idx is supposed to report whether it has updated

vq->avail_idx. Instead, it returns whether all entries have been

consumed, which is usually the same. But not always - in

drivers/vhost/net.c and when mergeable buffers have been enabled, the

driver checks whether the combined entries are big enough to store an

incoming packet. If not, the driver re-enables notifications with

available entries still in the ring. The incorrect return value from

vhost_get_avail_idx propagates through vhost_enable_notify and causes

the host to livelock if the guest is not making progress, as vhost will

immediately disable notifications and retry using the available entries.

This goes back to commit d3bb267bbdcb ("vhost: cache avail index in

vhost_enable_notify()") which changed vhost_enable_notify() to compare

the freshly read avail index against vq->last_avail_idx instead of the

previously cached vq->avail_idx. Commit 7ad472397667 ("vhost: move

smp_rmb() into vhost_get_avail_idx()") then carried over the same

comparison when refactoring vhost_enable_notify() to call the unified

vhost_get_avail_idx().

The obvious fix is to make vhost_get_avail_idx do what the comment

says it does and report whether new entries have been added. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References