HIGH Introduced in 5.5
net AltName Panic
CVE-2026-98073
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
KernelScan AI5.5MEDIUM
01Description
In the Linux kernel, the following vulnerability has been resolved: net: Remove conflicting altnames for dying netns in __dev_change_net_namespace(). syzbot reported the warning in cfg80211_pernet_exit(). [0] The repro does the following: 1. create two device in root netns and non-root netns 2. assign the same altname for the two devices 3. remove the non-root netns Since commit 7663d522099e ("net: check for altname conflicts when changing netdev's netns"), cfg80211_switch_netns() and cfg802154_switch_netns() fail if init_net has a device with the conflicting altname. default_device_exit_net() had the same issue and commit d09486a04f5d ("net: fix removing a namespace with conflicting altnames") fixed it. cfg80211_pernet_exit() and cfg802154_pernet_exit() need the same fix. Let's generalise the fix by removing conflicting altnames for dying netns in __dev_change_net_namespace(). [0]: cfg80211_switch_netns(rdev, &init_net) WARNING: net/wireless/core.c:1871 at cfg80211_pernet_exit+0xd5/0x120 net/wireless/core.c:1871, CPU#1: kworker/u8:9/1160 Modules linked in: CPU: 1 UID: 0 PID: 1160 Comm: kworker/u8:9 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: netns cleanup_net RIP: 0010:cfg80211_pernet_exit+0xd5/0x120 net/wireless/core.c:1871 Code: e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 b4 ef 0e f7 4d 8b 36 49 81 fe 20 10 4a 90 74 12 e8 03 3d 9f f6 eb 85 e8 fc 3c 9f f6 90 <0f> 0b 90 eb cc e8 f1 3c 9f f6 eb 05 e8 ea 3c 9f f6 5b 41 5c 41 5e RSP: 0018:ffffc900057a78f0 EFLAGS: 00010293 RAX: ffffffff8b287154 RBX: ffff88807ba72780 RCX: ffff8880213e8000 RDX: 0000000000000000 RSI: 00000000ffffffef RDI: 0000000000000000 RBP: 00000000ffffffef R08: ffffffff9024cc67 R09: 0000000000000000 R10: fffff52000af4eb0 R11: fffffbfff204998d R12: dffffc0000000000 R13: ffffffff904a1080 R14: ffff888144ed0008 R15: ffff888144ed0e20 FS: 0000000000000000(0000) GS:ffff888124de6000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005642de0a8a70 CR3: 000000007a40c000 CR4: 00000000003526f0 Call Trace: <TASK> ops_exit_list net/core/net_namespace.c:200 [inline] ops_undo_list+0x43d/0x8d0 net/core/net_namespace.c:253 cleanup_net+0x572/0x810 net/core/net_namespace.c:706 process_one_work kernel/workqueue.c:3387 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK>
02KernelScan AI Analysis
Risk summary
A local user with user-namespace access can trigger a kernel warning by assigning conflicting alternative interface names across network namespaces and then destroying the namespace. On systems with panic-on-warn enabled, this causes a kernel panic; otherwise, the failed cleanup leaves devices in an inconsistent state. The flaw requires only unprivileged local access when user namespaces are available.
Vulnerability analysis
When a network namespace containing a wireless or 802.15.4 device is destroyed, the kernel attempts to move that device back to the initial network namespace. If a device in the initial namespace already has the same alternative name, the move fails and triggers a kernel warning that can crash systems configured with panic-on-warn. The fix removes conflicting alternative names before attempting the namespace move when the source namespace is being torn down, ensuring cleanup always succeeds regardless of which subsystem owns the device. An unprivileged local user with user-namespace access can trigger this by creating a network namespace, assigning a conflicting alternative name to a device, and then deleting the namespace.
Lifecycle
03Fix Versions
| Branch | Introduced | Fixed in | Patch commit |
|---|---|---|---|
| 6.18 | 5.5 | 6.18.53 | a29ea5b50346 |
| 7.2 | 5.5 | 7.2.7 | ac6631843269 |
| mainline | 5.5 | 7.3-rc2 | debac3a20dec |