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CVE-2026-64093
batman-adv: tp_meter: directly shut down timer on cleanup
Published 2026-07-19 (3 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-2026-64093 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 | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed 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_sender_cleanup() was calling timer_delete_sync() followed by timer_delete() to guard against the timer handler re-arming itself between the two calls. This double-deletion hack relied on the sending status being set to 0 to suppress re-arming. Replace both calls with a single timer_shutdown_sync(). This function both waits for any running timer callback to complete (like timer_delete_sync()) and permanently disarms the timer so it cannot be re-armed afterwards, making re-arming prevention unconditional and self-documenting. The re-arming property is also required because otherwise: 1. context 0 (batadv_tp_recv_ack()) checks in batadv_tp_reset_sender_timer() if sending is still 1 -> it is 2. context 1 changes in batadv_tp_sender_shutdown() sending to 0 and in this process forces the kthread to stop timer in batadv_tp_sender_cleanup() 3. context 0 continues in batadv_tp_reset_sender_timer() and rearms the timer -> but the reference for it is already gone
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
- 2026-07-19 (3 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
- 0.35%, higher than 26.6% 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 | 5.15.210 | 00bf4bb9947b |
| 4.8 | 6.1.176 | 74a766340554 |
| 4.8 | 6.6.143 | 5bc2d50fb66b |
| 4.8 | 6.12.93 | f86b20ec8d17 |
| 4.8 | 6.18.34 | 770bf0a35f06 |
| 4.8 | 7.0.11 | 933880a8bc9b |
| 4.8 | 7.1 | d5487249a81e |
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
- The bug is triggered in batadv_tp_recv_ack() when forged or legitimate BATADV_TP_ACK mesh packets are received on a batman-adv hard interface; exploitation requires membership on the same batman-adv mesh (shared WiFi/ethernet logical network), which is Adjacent under CVSS and kernel WiFi guidance.
- AC:LAttack complexity, low
- This is a race between batadv_tp_recv_ack()/batadv_tp_reset_sender_timer() and batadv_tp_sender_cleanup(); an adjacent mesh attacker controls ACK timing and can flood packets to reliably hit the window between timer_delete_sync() and timer_delete() while the session tears down.
- PR:NPrivileges required, none
- The vulnerable receive path has no capability or authentication checks; any mesh peer can send TP ACK packets matching an active session without CAP_NET_ADMIN or other privileges on the victim (session start via netlink is a victim-side precondition, not attacker privilege).
- UI:NUser interaction, none
- Exploitation requires only attacker-timed mesh packets during session teardown; no victim end-user action (opening files, clicking links, etc.) is needed beyond normal mesh operation.
- S:UScope, unchanged
- Impact is a kernel heap use-after-free in batman-adv with potential privilege escalation; it does not cross a VM, container, or IOMMU security boundary.
- C:HConfidentiality impact, high
- Re-arming mod_timer() on a freed batadv_tp_vars after batadv_tp_vars_put() is a classic use-after-free; the attacker can influence freed heap contents and obtain arbitrary kernel memory read primitives.
- I:HIntegrity impact, high
- The UAF corrupts timer_list and adjacent kmalloc object fields; combined with heap grooming this enables arbitrary kernel writes and control-flow hijacking, not merely a bounded modification.
- A:HAvailability impact, high
- When the re-armed timer fires on freed memory, batadv_tp_sender_timeout() dereferences stale tp_vars pointers, causing kernel oops/panic and reliable remote denial of service even without full exploitation.