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CVE-2026-52931
batman-adv: tp_meter: avoid use of uninit sender vars
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-2026-52931 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_tp_recv_ack() and batadv_tp_stop() are only valid for tp_vars in the BATADV_TP_SENDER role. When called with a BATADV_TP_RECEIVER role, it proceeds to read sender-only members that were never initialized, leading to undefined behavior. This can be triggered when a node that is currently acting as a receiver in an ongoing tp_meter session receives a malicious ACK packet. Guard against this by checking tp_vars->role immediately after the lookup and bailing out if it is not BATADV_TP_SENDER, before any of those members are accessed.
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/tp_meter.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_advPrints 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
Signals
- Published
- 2026-06-24 (4 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.40%, higher than 32.6% 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 |
|---|---|---|
| 4.8 | 5.10.258 | 0e388af04b39 |
| 4.8 | 5.15.209 | 1a21c055f66e |
| 4.8 | 6.1.175 | 9884c9c02d3c |
| 4.8 | 6.6.142 | 53f931e0146a |
| 4.8 | 6.12.92 | ecdaa3e4d910 |
| 4.8 | 6.18.34 | dc2ae5fbd2da |
| 4.8 | 7.0.11 | 85397e48afe6 |
| 4.8 | 7.1 | 6c65cf23d4c6 |
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:NAttack vector, network
- The vulnerable code is reached by crafted BATMAN-adv ICMP TP packets received on an active batman-adv mesh interface and can be delivered by a remote mesh peer over the network. It is not a local-only netlink path and does not require physical access.
- AC:LAttack complexity, low
- No race or victim timing is required; the attacker controls the TP session creation packet and the follow-up malicious ACK. The requirement that batman-adv is active is an environmental precondition for the affected subsystem.
- PR:NPrivileges required, none
- The packet receive path has no credential or authentication check before `batadv_tp_meter_recv()` and `batadv_tp_recv_ack()`. A malicious peer can create the receiver-side tp_meter session with a TP MSG and then send a matching TP ACK.
- UI:NUser interaction, none
- Exploitation is driven entirely by attacker-sent network packets. No victim user action is required once the target batman-adv interface is active.
- S:UScope, unchanged
- The impact is within the vulnerable kernel instance and its batman-adv networking context. This is not a VM escape, IOMMU bypass, or cross-authority boundary violation.
- C:HConfidentiality impact, high
- The ACK path can operate on uninitialized sender-only state, including waitqueue/list/lock and counter fields, creating kernel memory corruption potential. Under conservative scoring, successful exploitation of that corruption can expose arbitrary kernel memory.
- I:HIntegrity impact, high
- The same uninitialized sender state can drive writes through corrupted kernel synchronization/list structures and sender counters. With heap grooming, this is defensible as a kernel memory corruption primitive capable of arbitrary modification or code execution.
- A:HAvailability impact, high
- At minimum, forged ACKs can dereference or manipulate uninitialized lock, list, timer, and waitqueue state, leading to kernel oops, panic, hang, or sustained denial of service. The trigger can be repeated by sending additional crafted packets.