CVE-2026-89948

What the bug is

When the mesh interface is getting deleted, then batadv_bla_del_backbone_claims() (via batadv_bla_purge_backbone_gw()) could make sure that all claims gets removed. But this function is only executed when bat_priv->bla.claim_hash is not NULL. And since batadv_bla_free() is always setting it to NULL before it is (indirectly) called, it was never actually executed. But the batadv_bla_purge_claims() -> batadv_handle_unclaim() is at the moment too fragile because the BLA code is not handling the rehashing in batadv_bla_update_orig_address(). The stored backbone address doesn't have to be the one actually used for the hash bucket selection during the initial adding of the backbone. The batadv_handle_unclaim() can therefore fail to find the respective backbone for the unclaim and then stop the deletion. But the actual backbone_gw object is not needed for the unclaim because all relevant information is always provided by the caller. And the check for the existence of the backbone_gw doesn't provide any additional security check for the deletion of a claim.

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/bridge_loop_avoidance.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_BLA' /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.

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

M

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

Build switches

CONFIG_BATMAN_ADV, CONFIG_BATMAN_ADV_BLA

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

0.21%, higher than 10.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

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
3.5	5.10.270	844a95a734f1
3.5	5.15.221	baeb1a28fd8e
3.5	6.1.188	aacffa780a37
3.5	6.6.157	76aedcde5a24
3.5	6.12.110	f50edb69082a
3.5	6.18.51	871acdf97f64
3.5	7.2.5	9a0c47023d32
3.5	7.3	8d128c932bce

Debian advisories