Look up another CVE · open CVE-2026-64218 in the interactive tracker
CVE-2026-64218
batman-adv: bla: fix report_work leak on backbone_gw purge
Published 2026-07-24 (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-2026-64218 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_bla_purge_backbone_gw() removes stale backbone gateway entries, but fails to properly handle their associated report_work: - If report_work is running, the purge must wait for it to finish before freeing the backbone_gw, otherwise the worker may access freed memory (e.g. bat_priv). - If report_work is pending, the purge must cancel it and release the reference held for that pending work item. The previous implementation called hlist_for_each_entry_safe() inside a spin_lock_bh() section, but cancel_work_sync() may sleep and therefore cannot be called from within a spinlock-protected region. Restructure the loop to handle one entry per spinlock critical section: acquire the lock, find the next entry to purge, remove it from the hash list, then release the lock before calling cancel_work_sync() and dropping the hash_entry reference. Repeat until no more entries require purging.
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_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 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
- 2026-07-24 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.3% 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 | 5.10.258 | ce2c0ee4d76d |
| 3.5 | 5.15.209 | 3423a45e5c3d |
| 3.5 | 6.1.175 | f1303adb1e59 |
| 3.5 | 6.6.142 | 48663158222b |
| 3.5 | 6.12.92 | eeddd7bab3d5 |
| 3.5 | 6.18.34 | c6de1a5a9c40 |
| 3.5 | 7.0.11 | 95a703466127 |
| 3.5 | 7.1 | 0459430add32 |
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:LAttack vector, local
- Although mesh packets can enqueue report_work, exploitation requires purging or tearing down the mesh object, which a local attacker can perform through netlink in a controlled network namespace.
- AC:LAttack complexity, low
- The attacker can observe the periodic loop-detect address, enqueue many VLAN-specific work items, and immediately delete the interface, controlling both sides of the race.
- PR:LPrivileges required, low
- Mesh configuration and teardown require CAP_NET_ADMIN, but batman-adv supports network namespaces and GENL_UNS_ADMIN_PERM, making the path reachable by an otherwise unprivileged user through user namespaces.
- UI:NUser interaction, none
- The attacker can create, trigger, and tear down the affected mesh interface without action from another user.
- S:UScope, unchanged
- Exploitation compromises the host kernel within its existing security authority; this is standard kernel privilege escalation rather than a VM or hardware-boundary escape.
- C:HConfidentiality impact, high
- The worker can dereference a freed bat_priv, net_device, and embedded kobject; controlled reallocation can turn these stale pointer chains into kernel-memory disclosure primitives.
- I:HIntegrity impact, high
- The use-after-free reaches kobject uevent processing and stale callback-bearing structures, making heap reuse and control-flow hijacking or arbitrary kernel modification plausible.
- A:HAvailability impact, high
- The stale net_device and kobject dereferences can cause a kernel oops or panic, and an attacker can repeat the trigger through user-namespace-created mesh interfaces.