CVE-2026-64423 ipv4: igmp: remove multicast group from hash table on device destruction

High 7.8 Published 25 Jul 2026 Updated 19 Oct 2026

A use-after-free in the Linux kernel IGMP module allows attackers to cause denial of service or execute code via concurrent device destruction and multicast access.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-64423?

CVE-2026-64423 is a high-severity use after free vulnerability in Linux kernel, published on 25 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

ipv4: igmp: remove multicast group from hash table on device destruction

When a device is destroyed under RTNL, ip_mc_destroy_dev() iterates through the multicast list and calls ip_ma_put() on each membership, scheduling them for RCU reclamation. However, they are not unlinked from the device's multicast hash table (mc_hash).

Since the device remains published in dev->ip_ptr until after ip_mc_destroy_dev() completes, concurrent RCU readers traversing mc_hash can still locate and access the multicast group after its refcount is decremented. If the RCU callback runs and frees the group while a reader is accessing it, a use-after-free occurs.

Fix this by unlinking the multicast group from mc_hash using ip_mc_hash_remove() before scheduling it for reclamation.

BUG: KASAN: slab-use-after-free in ip_check_mc_rcu+0x149/0x3f0 Read of size 4 at addr ffff888009bf1408 by task mausezahn/2276

Call Trace: <IRQ> dump_stack_lvl+0x67/0x90 print_report+0x175/0x7c0 kasan_report+0x147/0x180 ip_check_mc_rcu+0x149/0x3f0 udp_v4_early_demux+0x36d/0x12d0 ip_rcv_finish_core+0xb8b/0x1390 ip_rcv_finish+0x54/0x120 NF_HOOK+0x213/0x2b0 __netif_receive_skb+0x126/0x340 process_backlog+0x4f2/0xf00 __napi_poll+0x92/0x2c0 net_rx_action+0x583/0xc60 handle_softirqs+0x236/0x7f0 do_softirq+0x57/0x80 </IRQ>

Allocated by task 2239: kasan_save_track+0x3e/0x80 __kasan_kmalloc+0x72/0x90 ____ip_mc_inc_group+0x31a/0xa40 __ip_mc_join_group+0x334/0x3f0 do_ip_setsockopt+0x16fa/0x2010 ip_setsockopt+0x3f/0x90 do_sock_setsockopt+0x1ad/0x300

Freed by task 0: kasan_save_track+0x3e/0x80 kasan_save_free_info+0x40/0x50 __kasan_slab_free+0x3a/0x60 __rcu_free_sheaf_prepare+0xd4/0x220 rcu_free_sheaf+0x36/0x190 rcu_core+0x8d9/0x12f0 handle_softirqs+0x236/0x7f0

Weakness: CWE-416

Which versions are affected by CVE-2026-64423?

It affects 1 product.

Linux distribution packages (1)

kgraft-patch-SLE12-SP5_Update_86 SUSE:Linux Enterprise Live Patching 12 SP5 All versions 2-2.1

Products include Linux kernel.

How do I fix CVE-2026-64423?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-64423 being exploited?

There is no known exploitation of CVE-2026-64423 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as AZL-93737, BELL-CVE-2026-64423, DEBIAN-CVE-2026-64423, GHSA-wx6r-3m2q-4mm6, ROOT-OS-DEBIAN-12-CVE-2026-64423, ROOT-OS-UBUNTU-2204-CVE-2026-64423 and 2 more.