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CVE-2026-64413
netfilter: ebtables: zero chainstack array
Published 2026-07-25 (3 months ago) by the Linux kernel CNA. Subsystem net/bridge. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64413 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-4720-1 · 2026-08-05 · text | 6.1.180-1 | Update the kernel and reboot. DLA-4720-1 shipped the fix on 2026-08-05, in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6405-1 · 2026-07-31 · text | 6.12.100-1 | Update the kernel and reboot. DSA-6405-1 shipped the fix on 2026-07-31, in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
sashiko reports: looking at ebtables table translation, could a sparse cpu_possible_mask lead to an uninitialized pointer free? If cpu_possible_mask is sparse (for example, CPU 0 and CPU 2 are possible, but CPU 1 is not), the allocation loop skips CPU 1. If vmalloc_node() fails at CPU 2, the cleanup loop will blindly decrement and call vfree() on newinfo->chainstack[1]. Not a real-world bug, such allocation isn't expected to fail in the first place.
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/bridge/netfilter/ebtables.c
- What this is
- NETFILTERMAINTAINERS section matched on net/*/netfilter/ · netfilter-devel@vger.kernel.org · Maintained
- Kernel module
- ebtables
Check it on the machine
grep -wE 'CONFIG_BRIDGE|CONFIG_BRIDGE_NF_EBTABLES|CONFIG_BRIDGE_NF_EBTABLES_LEGACY|CONFIG_NETFILTER' /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 ebtablesPrints 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 does not build this code in 2 releases. It does build it in 3 releases, so the answer depends on which release the machine runs.
- bookworm, trixiem
- forky, sidn
- bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- n
- not enabled on any flavour - this release does not build the code
- Build switches
- CONFIG_BRIDGE, CONFIG_BRIDGE_NF_EBTABLES, CONFIG_BRIDGE_NF_EBTABLES_LEGACY, CONFIG_NETFILTER
- 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
- 2026-07-25 (3 months ago)source
- CVSS
- 7.0 high
CVSS:3.1/AV:L/AC:H/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 2.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/bridge
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.12 | 5.10.261 | 2ade612967e2 |
| 2.6.12 | 5.15.212 | 42bef500d07b |
| 2.6.12 | 6.1.178 | fc7f10545104 |
| 2.6.12 | 6.6.145 | 9e6c5169db42 |
| 2.6.12 | 6.12.97 | 29bf41a9b59a |
| 2.6.12 | 6.18.39 | 9f74d28e903f |
| 2.6.12 | 7.1.4 | 5ee856e4208a |
| 2.6.12 | 7.2 | cbfe53599eeb |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | tracker |
| DLA-4723-1 | 2026-08-07 | bullseye 6.1.180-1~deb11u1 | tracker |
| DLA-4720-1 | 2026-08-05 | bookworm 6.1.180-1 | tracker |
| DLA-4717-1 | 2026-08-05 | bullseye 5.10.262-1 | tracker |
| DSA-6405-1 | 2026-07-31 | trixie 6.12.100-1 | 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:LAttack vector, local
- The vulnerable translation path is reached through a local SOL_IP setsockopt(EBT_SO_SET_ENTRIES) call on an IPv4 socket, not through received network traffic.
- AC:HAttack complexity, high
- Exploitation requires a boot-fixed sparse cpu_possible_mask and a per-CPU vmalloc failure after an earlier allocation succeeds. Although memory pressure is attacker-influenceable, these uncommon conditions are not fully attacker-controlled.
- PR:LPrivileges required, low
- The path requires CAP_NET_ADMIN in the socket network namespace, which an unprivileged user can obtain through an owned user and network namespace where unprivileged user namespaces are enabled.
- UI:NUser interaction, none
- The attacker directly submits the crafted ebtables replacement; no victim action is required.
- S:UScope, unchanged
- This is ordinary user-namespace-to-kernel privilege escalation within the host security authority, without crossing a VM, hypervisor, or IOMMU boundary.
- C:HConfidentiality impact, high
- The uninitialized slot can alias a live vmalloc allocation, causing it to be freed and leaving its owner with a groomable use-after-free capable of exposing arbitrary kernel memory.
- I:HIntegrity impact, high
- Freeing a live vmalloc-backed kernel object can enable controlled reallocation, arbitrary memory modification, and kernel control-flow hijacking.
- A:HAvailability impact, high
- An invalid vfree can panic kernels configured with panic_on_warn, while freeing a live allocation creates a use-after-free that can crash or panic the kernel.