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CVE-2026-52934

batman-adv: tvlv: reject oversized TVLV packets

8.8 EPSS 0.2% AV:A

Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem net/batman-adv. Debian urgency: not yet assigned.

What to do, per Debian release

Debian's own status for CVE-2026-52934 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source

Release	Status	Version	What this means
Debian 12bookworm	fixedDLA-4665-1 · 2026-07-03 · text	6.1.176-1	Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts.
Debian 13trixie	fixed	6.12.94-1	Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts.
Debian 14forky	fixed	7.0.12-1	Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts.
Debian unstablesid	fixed	7.0.12-1	Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts.

The vulnerability

What the bug is

batadv_tvlv_container_ogm_append() builds a TVLV packet section from the tvlv.container_list. The total size of this section is computed by batadv_tvlv_container_list_size(), which sums the sizes of all registered containers. The return type and accumulator in batadv_tvlv_container_list_size() were u16. If the accumulated size exceeds U16_MAX, the value wraps around, causing the subsequent allocation in batadv_tvlv_container_ogm_append() to be undersized. The memcpy-style copy that follows would then write beyond the end of the allocated buffer, corrupting kernel memory. Fix this by widening the return type of batadv_tvlv_container_list_size() to size_t. In batadv_tvlv_container_ogm_append(), check the computed length against U16_MAX before proceeding, and bail out as if the allocation had failed when the limit is exceeded.

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/tvlv.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 -w CONFIG_BATMAN_ADV /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, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64

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

Build switch: CONFIG_BATMAN_ADV

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

Debian tracker CVE record NVD kernel CNA record

Signals

Published: 2026-06-24 (4 months ago)source
CVSS: 8.8 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it
Attack vector: adjacent network (AV:A)source
EPSS: 0.24%, higher than 14.5% 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
3.13	5.10.259	c02aa6c0c9d1
3.13	5.15.210	1595628a2f87
3.13	6.1.176	6448a49344e8
3.13	6.6.143	13493b00dd1e
3.13	6.12.93	94db72e9dac2
3.13	6.18.34	ede47988ac56
3.13	7.0.11	94a3d72cd9b2
3.13	7.1	f50487e35663

Debian advisories

Advisory	Date	Shipped to	Debian
DLA-4671-1	2026-07-05	bullseye 6.1.176-1~deb11u1	tracker
DLA-4665-1	2026-07-03	bookworm 6.1.176-1	tracker
DLA-4664-1	2026-07-03	bullseye 5.10.259-1	tracker

Why the CNA scored it this way

Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source

AV:AAttack vector, adjacent network: batman-adv is a layer-2 mesh/bridge subsystem, and the defensible remote path is from an attached same-link client or mesh segment causing local TT TVLV growth before periodic OGM generation. This is adjacent-network reachability rather than a routable Internet service.
AC:LAttack complexity, low: Once on the L2 segment in a vulnerable high-MTU/fragmentation deployment, the attacker can repeatedly emit frames with many source MACs and wait for the periodic OGM append path. No race or probabilistic condition is required.
PR:NPrivileges required, none: The attacker does not need a local account or kernel privileges on the vulnerable system in the adjacent-client scenario. Administrative netlink privileges are needed to deploy/configure batman-adv, but not to trigger TT learning on an already deployed node.
UI:NUser interaction, none: No victim user action is required after the vulnerable batman-adv node is configured and active. OGM generation is periodic kernel work.
S:UScope, unchanged: The corruption occurs in the vulnerable host kernel and affects resources under the same kernel security authority. This is not a VM escape, IOMMU bypass, or other cross-scope boundary.
C:HConfidentiality impact, high: The bug is a kernel heap out-of-bounds write from an undersized kmalloc buffer, with attacker-influenced TVLV/TT data. Such memory corruption is reasonably exploitable for information disclosure, so confidentiality is High.
I:HIntegrity impact, high: The memcpy-style overflow corrupts adjacent kernel heap memory and can plausibly be shaped into arbitrary write or code execution. Out-of-bounds kernel writes are scored as High integrity impact.
A:HAvailability impact, high: Even without full exploitation, the heap overflow can corrupt kernel memory and crash or panic the system. Availability impact is therefore High.