CVE-2026-93250

Status: UPDATED  |  Advisory ID: CVE-2026-93250

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

vxlan: mdb: Fix use-after-free in vxlan_mdb_flush()

vxlan_mdb_flush() iterates over the MDB entries using

hlist_for_each_entry_safe(), which only tolerates the removal of the

current entry. Contrary to the comment above the loop, the removal of an

entry can trigger the removal of another entry.

Flushing the remotes of a (*, G) entry also removes the (S, G) entries

that were created for its source list, once they are left without

remotes:

vxlan_mdb_remotes_flush()

-> vxlan_mdb_remote_del()

-> vxlan_mdb_remote_srcs_del()

-> vxlan_mdb_remote_src_del()

-> vxlan_mdb_remote_src_fwd_del()

-> __vxlan_mdb_del()

-> vxlan_mdb_entry_put()

Such an entry can be located after the (*, G) entry in the list, as

vxlan_mdb_entry_get() returns an existing entry without moving it to the

head of the list. This order is obtained by adding the (S, G) entry

before the (*, G) entry, the latter with NLM_F_REPLACE, as the addition

of the source otherwise fails with -EEXIST. The (S, G) entry is then the

entry saved by hlist_for_each_entry_safe() and it is freed while the

(*, G) entry is processed. The next iteration calls hlist_del() on it

again, writing LIST_POISON1 to LIST_POISON2 [1].

Besides device deletion, the flush is also reachable from RTM_DELMDB

with NLM_F_BULK.

Fix by re-reading the next entry after the remotes were flushed. The

current entry cannot be removed by this flush, as source lists can only

be configured on (*, G) entries and the removed entries are (S, G)

entries. It is therefore still linked and its next pointer reflects the

removals.

[1]

BUG: KASAN: wild-memory-access in vxlan_mdb_entry_put.part.0+0x328/0x588

Write of size 8 at addr dead000000000122 by task ip/327

CPU: 3 UID: 1000 PID: 327 Comm: ip Not tainted 7.2.0-rc7 #2 PREEMPT

Call trace:

vxlan_mdb_entry_put.part.0+0x328/0x588

vxlan_mdb_flush+0x1d8/0x25c

vxlan_mdb_fini+0x8c/0x100

vxlan_uninit+0x1c/0x7c

unregister_netdevice_many_notify+0x954/0xd4c

rtnl_dellink+0x210/0x530

rtnetlink_rcv_msg+0x434/0x4d0

netlink_rcv_skb+0xc4/0x204

rtnetlink_rcv+0x18/0x24

netlink_unicast+0x4b8/0x548

netlink_sendmsg+0x29c/0x560

____sys_sendmsg+0x390/0x3ec

___sys_sendmsg+0x114/0x188

__sys_sendmsg+0xf0/0x178

__arm64_sys_sendmsg+0x48/0x60

invoke_syscall.constprop.0+0x58/0x180

el0_svc_common.constprop.0+0x74/0x140

do_el0_svc+0x30/0x40

el0_svc+0x38/0x98

el0t_64_sync_handler+0xa0/0xe4

el0t_64_sync+0x198/0x19c (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References