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CVE-2026-64096
batman-adv: mcast: fix use-after-free in orig_node RCU release
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-2026-64096 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_mcast_purge_orig() removes entries from RCU-protected hlists but does not wait for an RCU grace period before returning. Concurrent RCU readers may still accesses references to those entries at the point of removal. RCU-protected readers trying to operate on entries like orig->mcast_want_all_ipv6_node will then access already freed memory. Fix this by moving batadv_mcast_purge_orig() to batadv_orig_node_release(), just before the call_rcu() invocation. This ensures RCU readers that were active at purge time have drained before the orig_node memory is reclaimed.
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/originator.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
- 0.26%, higher than 15.9% 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 |
|---|---|---|
| 3.15 | 5.10.258 | ff3a4487ead4 |
| 3.15 | 5.15.209 | 78a63fb2f7d5 |
| 3.15 | 6.1.175 | ced48f55bac7 |
| 3.15 | 6.6.142 | 70bcb678561f |
| 3.15 | 6.12.92 | aef897c9d2dd |
| 3.15 | 6.18.34 | 8a3707653ab6 |
| 3.15 | 7.0.11 | edfb1e094104 |
| 3.15 | 7.1 | 20c2d6a20ca9 |
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
- Exploitation requires injecting BATMAN-adv protocol frames onto the victim's mesh segment (typically WiFi or wired L2 mesh), reachable only from adjacent mesh peers rather than arbitrary remote Internet hosts.
- AC:LAttack complexity, low
- An attacker on the mesh controls both sides of the race by registering an originator with multicast flags via OGMs, ceasing heartbeats to trigger purge, and flooding IPv6 multicast to drive RCU readers in batadv_mcast_forw_want_all_ipv6().
- PR:NPrivileges required, none
- No local privileges on the victim are required; a rogue mesh peer can send OGMs and multicast traffic that drive originator creation, timeout purge, and concurrent RCU list traversal without authentication.
- UI:NUser interaction, none
- Exploitation is fully automated through mesh protocol packet exchange and does not require any action from a local user or administrator on the victim node.
- S:UScope, unchanged
- The use-after-free corrupts kernel heap memory within the same kernel security boundary and does not cross into other VMs, containers, or hardware isolation domains.
- C:HConfidentiality impact, high
- The use-after-free on batadv_orig_node allows concurrent RCU readers to dereference freed memory containing orig->mcast_want_all_ipv6_node and related fields, enabling arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- Use-after-free of the orig_node structure provides attacker-influencable freed heap slots that can be leveraged for arbitrary kernel writes and potential code execution via heap grooming.
- A:HAvailability impact, high
- Concurrent access to freed orig_node memory during RCU list traversal can cause kernel oops or panic, and UAF conditions inherently threaten system availability even before full exploitation.