CVE-2026-99117

Status: UPDATED  |  Advisory ID: CVE-2026-99117

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

net: bridge: mcast: don't truncate the port group walk on teardown

__br_multicast_disable_port_ctx() and br_multicast_del_port() walk

port->mglist with hlist_for_each_entry_safe(). However,

br_multicast_find_del_pg() can also delete other entries from the same

list through br_multicast_fwd_src_remove() or __fwd_del_star_excl().

If such an entry is the iterator's saved next node, hlist_del_init()

clears its ->next and terminates the walk early. The reproducer triggers

this in both teardown walks, leaving port groups in the bridge mdb with

a dangling ->key.port after del_nbp() frees the port:

BUG: KASAN: slab-use-after-free in __mdb_fill_info+0x1191/0x1320

__mdb_fill_info+0x1191/0x1320

br_mdb_dump+0x594/0xe40

rtnl_mdb_dump+0x1cf/0x5d0

Use hlist_del_init_rcu() to unlink the group while preserving ->next.

br_multicast_del_pg() and the teardown walks run under

br->multicast_lock. The GC worker must acquire the same lock before

detaching the group for destruction, so the node remains alive while

the walk uses the preserved pointer.

Preserving ->next means a walk can now reach a group that an earlier

iteration already deleted as a side effect. That group is off mp->ports,

so br_multicast_find_del_pg() would fall through its port scan and hit

the trailing WARN_ON(1). Skip such groups at the top of that helper: a

port group is put on port->mglist when it is created and only unlinked

when it is deleted, so hlist_unhashed() identifies exactly this case. (NVD)

What to Do

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

References