GHSA-8CCP-78HM-HX73
Vulnerability from github – Published: 2026-01-13 18:31 – Updated: 2026-01-13 18:31In the Linux kernel, the following vulnerability has been resolved:
mlxsw: spectrum_router: Fix neighbour use-after-free
We sometimes observe use-after-free when dereferencing a neighbour [1]. The problem seems to be that the driver stores a pointer to the neighbour, but without holding a reference on it. A reference is only taken when the neighbour is used by a nexthop.
Fix by simplifying the reference counting scheme. Always take a reference when storing a neighbour pointer in a neighbour entry. Avoid taking a referencing when the neighbour is used by a nexthop as the neighbour entry associated with the nexthop already holds a reference.
Tested by running the test that uncovered the problem over 300 times. Without this patch the problem was reproduced after a handful of iterations.
[1] BUG: KASAN: slab-use-after-free in mlxsw_sp_neigh_entry_update+0x2d4/0x310 Read of size 8 at addr ffff88817f8e3420 by task ip/3929
CPU: 3 UID: 0 PID: 3929 Comm: ip Not tainted 6.18.0-rc4-virtme-g36b21a067510 #3 PREEMPT(full) Hardware name: Nvidia SN5600/VMOD0013, BIOS 5.13 05/31/2023 Call Trace: dump_stack_lvl+0x6f/0xa0 print_address_description.constprop.0+0x6e/0x300 print_report+0xfc/0x1fb kasan_report+0xe4/0x110 mlxsw_sp_neigh_entry_update+0x2d4/0x310 mlxsw_sp_router_rif_gone_sync+0x35f/0x510 mlxsw_sp_rif_destroy+0x1ea/0x730 mlxsw_sp_inetaddr_port_vlan_event+0xa1/0x1b0 __mlxsw_sp_inetaddr_lag_event+0xcc/0x130 __mlxsw_sp_inetaddr_event+0xf5/0x3c0 mlxsw_sp_router_netdevice_event+0x1015/0x1580 notifier_call_chain+0xcc/0x150 call_netdevice_notifiers_info+0x7e/0x100 __netdev_upper_dev_unlink+0x10b/0x210 netdev_upper_dev_unlink+0x79/0xa0 vrf_del_slave+0x18/0x50 do_set_master+0x146/0x7d0 do_setlink.isra.0+0x9a0/0x2880 rtnl_newlink+0x637/0xb20 rtnetlink_rcv_msg+0x6fe/0xb90 netlink_rcv_skb+0x123/0x380 netlink_unicast+0x4a3/0x770 netlink_sendmsg+0x75b/0xc90 __sock_sendmsg+0xbe/0x160 _syssendmsg+0x5b2/0x7d0 _sys_sendmsg+0xfd/0x180 __sys_sendmsg+0x124/0x1c0 do_syscall_64+0xbb/0xfd0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 [...]
Allocated by task 109: kasan_save_stack+0x30/0x50 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x7b/0x90 __kmalloc_noprof+0x2c1/0x790 neigh_alloc+0x6af/0x8f0 ___neigh_create+0x63/0xe90 mlxsw_sp_nexthop_neigh_init+0x430/0x7e0 mlxsw_sp_nexthop_type_init+0x212/0x960 mlxsw_sp_nexthop6_group_info_init.constprop.0+0x81f/0x1280 mlxsw_sp_nexthop6_group_get+0x392/0x6a0 mlxsw_sp_fib6_entry_create+0x46a/0xfd0 mlxsw_sp_router_fib6_replace+0x1ed/0x5f0 mlxsw_sp_router_fib6_event_work+0x10a/0x2a0 process_one_work+0xd57/0x1390 worker_thread+0x4d6/0xd40 kthread+0x355/0x5b0 ret_from_fork+0x1d4/0x270 ret_from_fork_asm+0x11/0x20
Freed by task 154: kasan_save_stack+0x30/0x50 kasan_save_track+0x14/0x30 __kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x43/0x70 kmem_cache_free_bulk.part.0+0x1eb/0x5e0 kvfree_rcu_bulk+0x1f2/0x260 kfree_rcu_work+0x130/0x1b0 process_one_work+0xd57/0x1390 worker_thread+0x4d6/0xd40 kthread+0x355/0x5b0 ret_from_fork+0x1d4/0x270 ret_from_fork_asm+0x11/0x20
Last potentially related work creation: kasan_save_stack+0x30/0x50 kasan_record_aux_stack+0x8c/0xa0 kvfree_call_rcu+0x93/0x5b0 mlxsw_sp_router_neigh_event_work+0x67d/0x860 process_one_work+0xd57/0x1390 worker_thread+0x4d6/0xd40 kthread+0x355/0x5b0 ret_from_fork+0x1d4/0x270 ret_from_fork_asm+0x11/0x20
{
"affected": [],
"aliases": [
"CVE-2025-68801"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-01-13T16:16:02Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmlxsw: spectrum_router: Fix neighbour use-after-free\n\nWe sometimes observe use-after-free when dereferencing a neighbour [1].\nThe problem seems to be that the driver stores a pointer to the\nneighbour, but without holding a reference on it. A reference is only\ntaken when the neighbour is used by a nexthop.\n\nFix by simplifying the reference counting scheme. Always take a\nreference when storing a neighbour pointer in a neighbour entry. Avoid\ntaking a referencing when the neighbour is used by a nexthop as the\nneighbour entry associated with the nexthop already holds a reference.\n\nTested by running the test that uncovered the problem over 300 times.\nWithout this patch the problem was reproduced after a handful of\niterations.\n\n[1]\nBUG: KASAN: slab-use-after-free in mlxsw_sp_neigh_entry_update+0x2d4/0x310\nRead of size 8 at addr ffff88817f8e3420 by task ip/3929\n\nCPU: 3 UID: 0 PID: 3929 Comm: ip Not tainted 6.18.0-rc4-virtme-g36b21a067510 #3 PREEMPT(full)\nHardware name: Nvidia SN5600/VMOD0013, BIOS 5.13 05/31/2023\nCall Trace:\n \u003cTASK\u003e\n dump_stack_lvl+0x6f/0xa0\n print_address_description.constprop.0+0x6e/0x300\n print_report+0xfc/0x1fb\n kasan_report+0xe4/0x110\n mlxsw_sp_neigh_entry_update+0x2d4/0x310\n mlxsw_sp_router_rif_gone_sync+0x35f/0x510\n mlxsw_sp_rif_destroy+0x1ea/0x730\n mlxsw_sp_inetaddr_port_vlan_event+0xa1/0x1b0\n __mlxsw_sp_inetaddr_lag_event+0xcc/0x130\n __mlxsw_sp_inetaddr_event+0xf5/0x3c0\n mlxsw_sp_router_netdevice_event+0x1015/0x1580\n notifier_call_chain+0xcc/0x150\n call_netdevice_notifiers_info+0x7e/0x100\n __netdev_upper_dev_unlink+0x10b/0x210\n netdev_upper_dev_unlink+0x79/0xa0\n vrf_del_slave+0x18/0x50\n do_set_master+0x146/0x7d0\n do_setlink.isra.0+0x9a0/0x2880\n rtnl_newlink+0x637/0xb20\n rtnetlink_rcv_msg+0x6fe/0xb90\n netlink_rcv_skb+0x123/0x380\n netlink_unicast+0x4a3/0x770\n netlink_sendmsg+0x75b/0xc90\n __sock_sendmsg+0xbe/0x160\n ____sys_sendmsg+0x5b2/0x7d0\n ___sys_sendmsg+0xfd/0x180\n __sys_sendmsg+0x124/0x1c0\n do_syscall_64+0xbb/0xfd0\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n[...]\n\nAllocated by task 109:\n kasan_save_stack+0x30/0x50\n kasan_save_track+0x14/0x30\n __kasan_kmalloc+0x7b/0x90\n __kmalloc_noprof+0x2c1/0x790\n neigh_alloc+0x6af/0x8f0\n ___neigh_create+0x63/0xe90\n mlxsw_sp_nexthop_neigh_init+0x430/0x7e0\n mlxsw_sp_nexthop_type_init+0x212/0x960\n mlxsw_sp_nexthop6_group_info_init.constprop.0+0x81f/0x1280\n mlxsw_sp_nexthop6_group_get+0x392/0x6a0\n mlxsw_sp_fib6_entry_create+0x46a/0xfd0\n mlxsw_sp_router_fib6_replace+0x1ed/0x5f0\n mlxsw_sp_router_fib6_event_work+0x10a/0x2a0\n process_one_work+0xd57/0x1390\n worker_thread+0x4d6/0xd40\n kthread+0x355/0x5b0\n ret_from_fork+0x1d4/0x270\n ret_from_fork_asm+0x11/0x20\n\nFreed by task 154:\n kasan_save_stack+0x30/0x50\n kasan_save_track+0x14/0x30\n __kasan_save_free_info+0x3b/0x60\n __kasan_slab_free+0x43/0x70\n kmem_cache_free_bulk.part.0+0x1eb/0x5e0\n kvfree_rcu_bulk+0x1f2/0x260\n kfree_rcu_work+0x130/0x1b0\n process_one_work+0xd57/0x1390\n worker_thread+0x4d6/0xd40\n kthread+0x355/0x5b0\n ret_from_fork+0x1d4/0x270\n ret_from_fork_asm+0x11/0x20\n\nLast potentially related work creation:\n kasan_save_stack+0x30/0x50\n kasan_record_aux_stack+0x8c/0xa0\n kvfree_call_rcu+0x93/0x5b0\n mlxsw_sp_router_neigh_event_work+0x67d/0x860\n process_one_work+0xd57/0x1390\n worker_thread+0x4d6/0xd40\n kthread+0x355/0x5b0\n ret_from_fork+0x1d4/0x270\n ret_from_fork_asm+0x11/0x20",
"id": "GHSA-8ccp-78hm-hx73",
"modified": "2026-01-13T18:31:04Z",
"published": "2026-01-13T18:31:04Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-68801"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4a3c569005f42ab5e5b2ad637132a33bf102cc08"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/675c5aeadf6472672c472dc0f26401e4fcfbf254"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8b0e69763ef948fb872a7767df4be665d18f5fd4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c437fbfd4382412598cdda1f8e2881b523668cc2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ed8141b206bdcfd5d0b92c90832eeb77b7a60a0a"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
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- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.