---
id: "CVE-2026-98881"
kind: "vulnerability"
aliases: ["CVE-2026-98881"]
title: "Linux kernel: stale rcu_barrier in bridge code stalls network namespace cleanup"
severity: "unknown"
cvss: null
epss: 0.00215
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["bridge", "containers", "linux-kernel", "runtime"]
not_affected_if: ["no-bridge-devices"]
published_at: "2026-10-23T12:18:21+00:00"
first_seen_at: "2026-10-23T21:57:33+00:00"
updated_at: "2026-10-25T12:38:51+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98881", "first_seen_at": "2026-10-23T21:57:33+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-98881", "first_seen_at": "2026-10-25T12:38:51+00:00"}]
---

# Linux kernel: stale rcu_barrier in bridge code stalls network namespace cleanup

A leftover rcu_barrier() call in the Linux kernel bridge multicast teardown path blocks network namespace cleanup for long periods, holding the RTNL lock. The sources describe a stall and lock pressure rather than code execution or data theft.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98881
- 2026-10-25T12:38:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-98881

## From the sources

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

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_