In the Linux kernel, the following vulnerability has been resolved:
macvlan: fix error recovery in macvlancommonnewlink()
valis provided a nice repro to crash the kernel:
ip link add p1 type veth peer p2 ip link set address 00:00:00:00:00:20 dev p1 ip link set up dev p1 ip link set up dev p2
ip link add mv0 link p2 type macvlan mode source ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20
ping -c1 -I p1 1.2.3.4
He also gave a very detailed analysis:
<quote valis>
The issue is triggered when a new macvlan link is created with MACVLANMODESOURCE mode and MACVLANMACADDRADD (or MACVLANMACADDRSET) parameter, lower device already has a macvlan port and registernetdevice() called from macvlancommon_newlink() fails (e.g. because of the invalid link name).
In this case macvlanhashaddsource is called from macvlanchangesources() / macvlancommon_newlink():
This adds a reference to vlan to the port's vlansourcehash using macvlansourceentry.
vlan is a pointer to the priv data of the link that is being created.
When registernetdevice() fails, the error is returned from macvlannewlink() to rtnlnewlinkcreate():
if (ops->newlink)
err = ops->newlink(dev, ¶ms, extack);
else
err = register_netdevice(dev);
if (err < 0) {
free_netdev(dev);
goto out;
}
and freenetdev() is called, causing a kvfree() on the struct netdevice that is still referenced in the source entry attached to the lower device's macvlan port.
Now all packets sent on the macvlan port with a matching source mac address will trigger a use-after-free in macvlanforwardsource().
</quote valis>
With all that, my fix is to make sure we call macvlanflushsources() regardless of @create value whenever "goto destroymacvlanport;" path is taken.
Many thanks to valis for following up on this issue.
{
"cna_assigner": "Linux",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23209.json"
}