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CVE-2026-52912
netfilter: nf_queue: hold bridge skb->dev while queued
Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem include/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-52912 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
br_pass_frame_up() rewrites skb->dev from the ingress port to the bridge master before queueing bridge LOCAL_IN packets. NFQUEUE only holds references on state.in/out and bridge physdevs, so a queued bridge packet can retain a freed bridge master in skb->dev until reinjection. When the verdict is reinjected later, br_netif_receive_skb() re-enters the receive path with skb->dev still pointing at the freed bridge master, triggering a use-after-free. Store skb->dev in the queue entry, hold a reference on it for the queue lifetime, and use the saved device when dropping queued packets during NETDEV_DOWN handling.
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.
include/net/netfilter/nf_queue.h
net/netfilter/nf_queue.c
net/netfilter/nfnetlink_queue.c
- What this is
- NETFILTERMAINTAINERS section matched on include/net/netfilter/ · netfilter-devel@vger.kernel.org · Maintained
Check it on the machine
grep -w 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.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_NETFILTER
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
- 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
- 0.16%, higher than 4.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- include/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.7 | 5.10.259 | 950d809f154d |
| 4.7 | 5.15.209 | a698ac8ab256 |
| 4.7 | 6.1.175 | 19924bdd8a45 |
| 4.7 | 6.6.142 | 1e5e20031c5e |
| 4.7 | 6.12.92 | 3823c27099cf |
| 4.7 | 6.18.34 | 15d464265120 |
| 4.7 | 7.0.11 | 3fb0f5c0f641 |
| 4.7 | 7.1 | e196115ec330 |
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:LAttack vector, local
- Exploitation requires local control of netfilter/NFQUEUE, bridge device lifecycle, and verdict reinjection through netlink/rtnetlink paths. Remote packets alone cannot force the needed bridge teardown and userspace verdict sequence.
- AC:LAttack complexity, low
- A local attacker can deterministically create a namespace, bridge/veth setup, NFQUEUE rule, queued packet, bridge teardown, and reinjection. There is no race dependent on conditions outside attacker control.
- PR:LPrivileges required, low
- The setup requires CAP_NET_ADMIN, but netfilter and bridge configuration are reachable with CAP_NET_ADMIN inside a user-created network namespace on systems allowing unprivileged user namespaces. This is Low, not High.
- UI:NUser interaction, none
- No victim action is required once the local attacker runs the exploit sequence. The attacker controls packet injection, queueing, device teardown, and verdict delivery.
- S:UScope, unchanged
- The impact is kernel memory corruption within the same host security authority. This is a standard local kernel privilege escalation/DoS scenario, not a VM or hardware boundary escape.
- C:HConfidentiality impact, high
- The bug is a use-after-free of the bridge master net_device retained in skb->dev across NFQUEUE. Kernel UAFs can be leveraged for kernel memory disclosure, so confidentiality impact is High.
- I:HIntegrity impact, high
- The stale net_device pointer is dereferenced after free in the receive path and can plausibly be combined with heap reclaim/spraying for memory corruption or control-flow impact. As a kernel UAF, integrity impact is High.
- A:HAvailability impact, high
- At minimum, reinjection can dereference freed net_device memory in netif_receive_skb and crash/oops the kernel. Repeated local triggering makes availability impact High.