---
id: CVE-2026-74543
title: 'net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()

  syzbot reported a memory leak [1] in the UDP tunnel NIC offload code.

  When device registration fails (…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 <
    52c753b46265243406690d980faa9514d3f53827
  - >-
    Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 <
    b712da45bd9b9835d132e9fbc0c3e43c164cb1fd
  - >-
    Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 <
    f82a2ded3d7a9098267c84f14eafdb98c4550ac5
  - >-
    Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 <
    b322532a4b774db1b480a2de84125910a70739a5
  - >-
    Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 <
    080695e6f005e2396f1207fd69d24c442cb230c6
  - Linux 5.9
published: '2026-08-15'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:45:53.873Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-74543'
references:
  - url: 'https://git.kernel.org/stable/c/52c753b46265243406690d980faa9514d3f53827'
  - url: 'https://git.kernel.org/stable/c/b712da45bd9b9835d132e9fbc0c3e43c164cb1fd'
  - url: 'https://git.kernel.org/stable/c/f82a2ded3d7a9098267c84f14eafdb98c4550ac5'
  - url: 'https://git.kernel.org/stable/c/b322532a4b774db1b480a2de84125910a70739a5'
  - url: 'https://git.kernel.org/stable/c/080695e6f005e2396f1207fd69d24c442cb230c6'
tags:
  - cve.org
epss: 0.00174
epssPercentile: 0.06506
ingestedAt: '2026-10-21T12:48:53.579Z'
---

## Overview

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

net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()

syzbot reported a memory leak [1] in the UDP tunnel NIC offload code.

When device registration fails (e.g. in register_netdevice()), netdev core
unwinds by sending a single NETDEV_UNREGISTER notification. If work was queued
during NETDEV_REGISTER (utn->work_pending is set), udp_tunnel_nic_unregister()
returns early:

	if (utn->work_pending)
		return;

Because failed registrations do not enter netdev_wait_allrefs_any(), no
subsequent NETDEV_UNREGISTER rebroadcast will ever occur. As a result, the
struct udp_tunnel_nic allocated in udp_tunnel_nic_alloc() is leaked
permanently.

Fix this by removing the early return. Instead, synchronously cancel any
pending work with cancel_delayed_work_sync() before freeing @utn.

To be able to call cancel_delayed_work_sync() while holding RTNL (the work also
needs RTNL), switch udp_tunnel_nic_device_sync_work() to rtnl_trylock(). If RTNL
is contended, requeue the work with a 1 jiffy delay (via queue_delayed_work())
to prevent high CPU contention while waiting for RTNL lock.

The utn->work_pending bookkeeping is no longer needed and is removed, as
the workqueue core already tracks the pending/running state of the work.

[1]
BUG: memory leak
unreferenced object 0xffff888127d5f840 (size 96):
  comm "syz-executor", pid 5806, jiffies 4294942188
  backtrace (crc 99fdb6c8):
    __kmalloc_noprof+0x3bf/0x550
    udp_tunnel_nic_alloc net/ipv4/udp_tunnel_nic.c:756 [inline]
    udp_tunnel_nic_register net/ipv4/udp_tunnel_nic.c:833 [inline]
    udp_tunnel_nic_netdevice_event+0x804/0xab0 net/ipv4/udp_tunnel_nic.c:931
    notifier_call_chain+0x59/0x160 kernel/notifier.c:85
    call_netdevice_notifiers_info+0x7d/0xb0 net/core/dev.c:2250
    register_netdevice+0xc10/0xeb0 net/core/dev.c:11478

## Affected

- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < 52c753b46265243406690d980faa9514d3f53827`
- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < b712da45bd9b9835d132e9fbc0c3e43c164cb1fd`
- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < f82a2ded3d7a9098267c84f14eafdb98c4550ac5`
- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < b322532a4b774db1b480a2de84125910a70739a5`
- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < 080695e6f005e2396f1207fd69d24c442cb230c6`
- `Linux 5.9`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.