CVE-2025-39796

  • Published: 2025-09-12T16:15:33.987

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

net: lapbether: ignore ops-locked netdevs

Syzkaller managed to trigger lock dependency in xsk_notify via
register_netdevice. As discussed in [0], using register_netdevice
in the notifiers is problematic so skip adding lapbeth for ops-locked
devices.

xsk_notifier+0xa4/0x280 net/xdp/xsk.c:1645
notifier_call_chain+0xbc/0x410 kernel/notifier.c:85
call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
call_netdevice_notifiers net/core/dev.c:2282 [inline]
unregister_netdevice_many_notify+0xf9d/0x2700 net/core/dev.c:12077
unregister_netdevice_many net/core/dev.c:12140 [inline]
unregister_netdevice_queue+0x305/0x3f0 net/core/dev.c:11984
register_netdevice+0x18f1/0x2270 net/core/dev.c:11149
lapbeth_new_device drivers/net/wan/lapbether.c:420 [inline]
lapbeth_device_event+0x5b1/0xbe0 drivers/net/wan/lapbether.c:462
notifier_call_chain+0xbc/0x410 kernel/notifier.c:85
call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
call_netdevice_notifiers net/core/dev.c:2282 [inline]
__dev_notify_flags+0x12c/0x2e0 net/core/dev.c:9497
netif_change_flags+0x108/0x160 net/core/dev.c:9526
dev_change_flags+0xba/0x250 net/core/dev_api.c:68
devinet_ioctl+0x11d5/0x1f50 net/ipv4/devinet.c:1200
inet_ioctl+0x3a7/0x3f0 net/ipv4/af_inet.c:1001

0: https://lore.kernel.org/netdev/20250625140357.6203d0af@kernel.org/

Related CVE by CWE

No related CWE found.

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How to fix CVE-2025-39796

CVE-2025-39796 is a unknown severity vulnerability affecting the affected product.

Description: In the Linux kernel, the following vulnerability has been resolved: net: lapbether: ignore ops-locked netdevs Syzkaller managed to trigger lock dependency in xsk_notify via register_netdevice. As discussed in [0], using register_netdevice in the notifiers is problematic so skip adding lapbeth for ops-locked devices. xsk_notifier+0xa4/0x280 net/xdp/xsk.c:1645 notifier_call_chain+0xbc/0x410 kernel/notifier.c:85 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230 call_netdevice_notifiers_extack net/core/dev.c:2268 [inline] call_netdevice_notifiers net/core/dev.c:2282 [inline] […]

Exploit Difficulty: HARD
⏱️ Time to exploit: > 4 hours
🛠️ Required skills: Advanced security expertise
💰 Public exploits: Rare or not public

How to Fix:

1 Identify affected systems

- Check if you're running the affected product

2 Immediate actions

- Update to the latest patched version
- If patching is not immediately possible: restrict network exposure, apply least-privilege access

3 Verification

- Test the fix in a staging environment first
- Review logs for signs of exploitation
- Monitor for IOCs (Indicators of Compromise)

4 Long-term prevention

- Enable automatic security updates
- Set up vulnerability monitoring
- Review and harden security configurations

Vendor Advisory: https://lore.kernel.org/netdev/20250625140357.6203d0af@kernel.org/

Exploit Difficulty Assessment

HARD
⏱️ Time to Exploit: > 4 hours
🛠️ Skills Required: Advanced security expertise
💰 Public Exploits: Rare or not public

Vulnerability Timeline

Sep 12, 2025
Vulnerability Published

CVE details first published to NVD database

Nov 12, 2025
Imported to Database

Added to this CVE tracking system

Detection Rules & IOCs

No specific detection rules generated for this vulnerability type.

No vendor/product data available.