CVE-2026-74356: Linux Vulnerability (CVSS 7.4)

Description

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.

Metrics

CVSS 3.1

7.4/10

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS Probability

0.17%

6.4th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= d3bb267bbdcba199568f1325743d9d501dea0560, < e115471008111f894c6528d9ab2ce7d0ce306f35; >= d3bb267bbdcba199568f1325743d9d501dea0560, < 7f229d27bf27c7e589eca690d8612763a7a4801f; >= d3bb267bbdcba199568f1325743d9d501dea0560, < a9326b652bc7acd748d7a1143573845c7924d847; >= d3bb267bbdcba199568f1325743d9d501dea0560, < 09861858a68342f851f71c669ac0f69865c32151
Linux	Linux	5.18

References

Timeline

Published: Aug 15, 2026
Last Modified: Aug 17, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-74356?

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.

How severe is CVE-2026-74356?

CVE-2026-74356 has a CVSS score of 7.4/10 (HIGH severity). The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-74356?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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