CVE-2026-74580

What the bug is

vq->meta_iotlb[] caches the vhost_iotlb_map that backs each vring metadata region, and iotlb_access_ok() returns early on a cache hit, taking the hit as proof that the region has already been validated: if (vhost_vq_meta_fetch(vq, addr, len, type)) return true; The cache is reset on VHOST_IOTLB_UPDATE and VHOST_IOTLB_INVALIDATE, on device IOTLB (re)initialisation and on vq reset, but not when VHOST_SET_VRING_ADDR replaces vq->desc, vq->avail and vq->used, nor when VHOST_SET_VRING_NUM changes the region sizes. With a device IOTLB attached both ioctls are accepted while the vq is live, and neither validates the addresses at ioctl time: vq_access_ok() and vq_log_used_access_ok() return true early because the addresses are GIOVAs, deferring validation to prefetch time. Once the cache has been populated that deferred validation no longer runs -- vq_meta_prefetch() hits the stale entry and returns true -- and vhost_vq_meta_fetch() keeps translating through the old mapping as map->addr + addr - map->start for an address the mapping no longer covers. vhost_copy_to_user() and vhost_copy_from_user() consume the result with __copy_to_user() and __copy_from_user(), which do not check it either, so a subsequent used ring update or descriptor fetch accesses memory outside the region the IOTLB actually maps. Reset the metadata cache whenever the vring is reconfigured, so the new addresses are pushed back through iotlb_access_ok()'s slow path.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/vhost/vhost.c

What this is

VIRTIO HOST (VHOST)MAINTAINERS section matched on drivers/vhost/ · kvm@vger.kernel.org · Maintained

Kernel module

none to look for. The file would have gone into vhost, and Debian does not compile it into that module, so finding vhost in lsmod would say nothing about this CVE.

Check it on the machine

grep -wE 'CONFIG_VHOST|CONFIG_VHOST_IOTLB|CONFIG_VHOST_RING' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian does not build this code. In 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.

• bookworm, trixie, forky, sid, bookworm · linux-6.12n

n

not enabled on any flavour - this release does not build the code

Build switches

CONFIG_VHOST, CONFIG_VHOST_IOTLB, CONFIG_VHOST_RING

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-08-21 (2 months ago)source

CVSS

8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it

Attack vector

local (AV:L)source

EPSS

0.13%, higher than 2.1% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/vhost

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
4.11	5.10.265	5224bd37e37d
4.11	5.15.216	54617e9119be
4.11	6.1.183	13fa6f32a56a
4.11	6.6.152	cf363a7a02ce
4.11	6.12.104	6fa3e9b1fe85
4.11	6.18.45	f1e21108e3dd
4.11	7.1.9	b70ebe0bba25
4.11	7.2	de845981da67

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