CVE-2026-89716

What the bug is

We must validate user-supplied deflate winbits before we pass it to zlib_deflate_workspacesize(), which triggers BUG_ON() if winbits value is outside of valid ranges.

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/zram/backend_deflate.c

What this is

ZRAM COMPRESSED RAM BLOCK DEVICE DRVIERMAINTAINERS section matched on drivers/block/zram/ · linux-kernel@vger.kernel.org · Maintained

Kernel module

zram

Check it on the machine

grep -wE 'CONFIG_ZRAM|CONFIG_ZRAM_BACKEND_DEFLATE' /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 zram

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 with an answer 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. The build rule could not be established for 1 release, so nothing is claimed about those.

• bookworm?
• trixie, forky, sidm

?

not established - no Makefile entry for the affected file

m

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

Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.

Build switches

CONFIG_ZRAM, CONFIG_ZRAM_BACKEND_DEFLATE

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

2026-09-11 (37 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.21%, higher than 10.0% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

unimportantsource

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
6.16	6.18.50	923578d0f0d0
6.16	7.2.4	e23fac4ab2a5
6.16	7.3	ec7607ac4717