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CVE-2026-68432

vxlan: require CAP_NET_ADMIN in the device netns for changelink

8.8 EPSS 0.1% AV:L

Published 2026-08-12 (2 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: not yet assigned.

What to do, per Debian release

Debian's own status for CVE-2026-68432 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-4777-1 · 2026-09-08 · text	6.1.187-1	Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts.
Debian 13trixie	fixed	6.12.101-1	Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts.
Debian 14forky	fixed	7.1.6-1	Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts.
Debian unstablesid	fixed	7.1.6-1	Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts.
Debian 12bookworm · linux-6.12	fixedDLA-4745-1 · 2026-08-18 · text	6.12.101-1~deb12u1	Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts.

The vulnerability

What the bug is

A tunnel changelink() operates on at most two netns, dev_net(dev) and the sticky underlay netns vxlan->net. They differ once the device is created in or moved to a netns other than the one the request runs in. The rtnl changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a caller privileged there but not in vxlan->net can rewrite a vxlan device whose underlay lives in vxlan->net. vxlan_changelink() validates and applies the new configuration against vxlan->net (vxlan_config_validate(vxlan->net, ...)) and can reopen the underlay socket in that netns, so the same reasoning as the tunnel changelink series applies here. Gate vxlan_changelink() with rtnl_dev_link_net_capable(), at the top of the op before any attribute is parsed, matching ipgre_changelink() and the rest of the "require CAP_NET_ADMIN in the device netns for changelink" series. Found by 0sec automated security-research tooling (https://0sec.ai).

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.

drivers/net/vxlan/vxlan_core.c

What this is: NETWORKING DRIVERSMAINTAINERS section matched on drivers/net/ · netdev@vger.kernel.org · Maintained
Kernel module: vxlan

Check it on the machine

grep -w CONFIG_VXLAN /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 vxlan

Prints 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 as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.

bookworm, trixie, forky, sid, bookworm · linux-6.12m

m: a loadable module on every flavour - check lsmod, can be blacklisted

Build switch: CONFIG_VXLAN

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

Debian tracker CVE record NVD kernel CNA record

Signals

Published: 2026-08-12 (2 months ago)source
CVSS: 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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: drivers/net

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
4.11	5.10.265	b95a8743e58f
4.11	5.15.216	7465ade989ba
4.11	6.1.183	0aa580a8bbbe
4.11	6.6.148	b3793d7dccb1
4.11	6.12.101	32d10c46bfde
4.11	6.18.42	730c7e5fea7f
4.11	7.1.6	e8ad0d311e22
4.11	7.2	3a61bd9637f3

Debian advisories

Advisory	Date	Shipped to	Debian
DLA-4777-1	2026-09-08	bookworm 6.1.187-1	tracker
DLA-4745-1	2026-08-18	bookworm 6.12.101-1~deb12u1	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 issuing an RTM_NEWLINK changelink request over an rtnetlink socket on the local system, matching the kernel guidance that netlink configuration paths are Local.
AC:LAttack complexity, low: Once a cross-namespace vxlan device is present in the caller's netns, the missing check is bypassed by a single deterministic netlink changelink call with no race, timing, or memory-layout dependency.
PR:LPrivileges required, low: The rtnl entry path only requires CAP_NET_ADMIN in dev_net(dev), which an unprivileged user obtains inside a user namespace via unshare --user --map-root-user --net; no privilege in the underlay netns vxlan->net is needed.
UI:NUser interaction, none: The attack is fully programmatic through netlink from the attacker's own process; no victim action such as mounting, opening a file, or clicking is required.
S:CScope, changed: Authorization is evaluated against dev_net(dev) while the configuration is validated and applied against vxlan->net, so the impact crosses from the attacker's net/user namespace into another tenant's or the host's network namespace.
C:HConfidentiality impact, high: The attacker can rewrite IFLA_VXLAN_GROUP/LOCAL and the underlay IFLA_VXLAN_LINK so encapsulated overlay traffic in the victim netns is sent to an attacker-controlled endpoint, exposing tunneled payloads.
I:HIntegrity impact, high: Unauthorized changelink mutates live tunnel state in the victim underlay netns (remote/local addresses, lower device, TOS/TTL/label, learning and proxy/RSC flags, default-remote FDB entries), enabling redirection and injection of overlay traffic.
A:HAvailability impact, high: Rewriting the remote group, source address, or lower device tears down and re-establishes multicast group membership and forwarding state, causing sustained loss of connectivity for every service riding the affected VXLAN overlay.