CVE-2026-64423

Analyzed Analyzed - Analysis Complete

Use-After-Free in Linux Kernel IPv4 IGMP Multicast Handling

Publication date: 2026-07-25

Last updated on: 2026-09-08

Assigner: kernel.org

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

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Meta Information

Published

2026-07-25

Last Modified

2026-09-08

Generated

2026-09-24

AI Q&A

2026-07-25

EPSS Evaluated

2026-09-23

NVD

CVE-2026-64423

EUVD

EUVD-2026-48967

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	From 5.11 (inc) to 5.15.212 (exc)
linux	linux_kernel	From 5.16 (inc) to 6.1.178 (exc)
linux	linux_kernel	From 6.2 (inc) to 6.6.145 (exc)
linux	linux_kernel	From 6.7 (inc) to 6.12.96 (exc)
linux	linux_kernel	From 6.13 (inc) to 6.18.39 (exc)
linux	linux_kernel	From 6.19 (inc) to 7.1.4 (exc)
linux	linux_kernel	7.2
linux	linux_kernel	7.2
linux	linux_kernel	From 3.11 (inc) to 5.10.261 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-416	The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Attack-Flow Graph

Executive Summary

This is a use-after-free vulnerability in the Linux kernel's IPv4 multicast group handling. When a network device is destroyed, multicast group references are not properly removed from the device's multicast hash table before being freed. This allows concurrent access to freed memory, leading to potential crashes or arbitrary code execution.

Detection Guidance

This vulnerability involves a use-after-free in the Linux kernel's IPv4 multicast handling. Detection requires kernel-level monitoring for slab-use-after-free errors in the ip_check_mc_rcu function. Check kernel logs for KASAN reports indicating use-after-free in multicast group handling. Commands like dmesg | grep -i kasan or journalctl -k | grep -i kasan may help identify such errors.

Impact Analysis

This vulnerability could allow an attacker to cause system crashes or execute arbitrary code with kernel privileges. It specifically affects systems using IPv4 multicast networking. The impact depends on whether the affected system uses multicast features and if an attacker can trigger device destruction while accessing the freed memory.

Compliance Impact

This vulnerability is a use-after-free flaw in the Linux kernel's IPv4 multicast handling. It does not directly impact compliance with standards like GDPR or HIPAA, as those focus on data protection, privacy, and security controls rather than kernel-level memory management issues.

Mitigation Strategies

Apply the kernel patch that unlinks multicast groups from the hash table before reclamation. Update to a Linux kernel version containing the fix. If immediate patching is not possible, restrict network operations involving multicast groups until the patch is applied.

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