CVE-2026-90187

What the bug is

null_init_zoned_dev() allocates dev->zones when a zoned device is powered on, but null_del_dev() never frees it on power-off; dev->zones is only freed later in null_free_dev(), when the configfs directory is removed. If the device is powered off and then on again, null_init_zoned_dev() allocates a new array and overwrites the dev->zones pointer, leaking the previous allocation each power cycle. Free dev->zones in null_del_dev() via null_free_zoned_dev() to solve it. And calling null_free_zoned_dev() in null_free_dev() is no longer necessary because every caller already invokes null_del_dev() first: via nullb_group_drop_item() before nullb_device_release(), in the null_add_dev() error path of null_create_dev(), and in null_destroy_dev(). Remove the redundant call. And take &lock around zone_cond_store() in the two store wrappers to serialize dev->zones check-and-deref against its alloc/free, which already run under &lock. The reason there was no problem before is that only nullb_device_release() or null_exit() frees the dev->zones, which guarantees that subsequent users won't access the configfs interface.

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/block/null_blk/main.c

What this is

BLOCK LAYERMAINTAINERS section matched on drivers/block/ · linux-block@vger.kernel.org · Maintained

Kernel module

null_blk

Check it on the machine

grep -w CONFIG_BLK_DEV_NULL_BLK /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.

lsmod | grep -w null_blk

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.

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

m

a loadable module on every flavour - check lsmod, can be blacklisted

Build switch

CONFIG_BLK_DEV_NULL_BLK

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

2026-09-17 (31 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.20%, higher than 9.2% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/block

Upstream fixes

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

Introduced	Fixed in	Commit
4.19	6.12.110	056be41932c9
4.19	6.18.52	b2437d37fcc3
4.19	7.2.6	0a3afab87124
4.19	7.3	2a6357a9b935

Debian advisories