CVE-2026-89950

What the bug is

batadv_mcast_forw_packet() and batadv_mcast_forw_scrape() is not only called (indirectly) by the unsharing+linearizing batadv_recv_mcast_packet() handler. When it is called (indirectly) by batadv_mcast_forw_mcsend() then it will be unshared but not linearized. The SKB_LINEAR_ASSERT() can therefore cause a fatal BUG(). The linearization should happen during the expansion of the head because the scrape function can be hit already during the initial batadv_mcast_forw_mode() selection code: * batadv_interface_tx * batadv_mcast_forw_mode * batadv_mcast_forw_mode_by_count() * batadv_mcast_forw_push() -> calls batadv_mcast_forw_expand_head() before everything else * batadv_mcast_forw_push_tvlvs() * batadv_mcast_forw_push_dests() * batadv_mcast_forw_push_adjust_padding() * batadv_mcast_forw_scrape()

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.

net/batman-adv/multicast_forw.c

What this is

BATMAN ADVANCEDMAINTAINERS section matched on net/batman-adv/ · b.a.t.m.a.n@lists.open-mesh.org · Maintained

Kernel module

batman_adv

Check it on the machine

grep -wE 'CONFIG_BATMAN_ADV|CONFIG_BATMAN_ADV_MCAST' /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 batman_adv

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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed. The build rule could not be established for 1 release, so nothing is claimed about those.

• bookworm?
• trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64

?

not established - no Makefile entry for the affected file

M

a module where it is built at all; some flavours do not build it

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_BATMAN_ADV, CONFIG_BATMAN_ADV_MCAST

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

2026-09-16 (33 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

unimportantsource

Subsystem

net/batman-adv

Upstream fixes

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

Introduced	Fixed in	Commit
6.8	6.12.110	a9603e0a7cb5
6.8	6.18.51	c32e5e25c412
6.8	7.2.5	2879177539e3
6.8	7.3	6a30a59e2660

Debian advisories