Cloudanix VulnDB

CVE-2025-38019

None

CVSS

—

EPSS

0.2%

Published

Jun 18, 2025

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A bug in Linux network handling with certain tunnel devices can cause the system to crash or allow unauthorized code execution when those devices are removed.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Moderate
Impact
Full Compromise
Component
OS kernel
Class
Use After Free
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

Use-after-free in mlxsw spectrum_router when replaying neighbor entries for GRE net devices during driver reload, causing the driver to retain references to freed memory that are later accessed on net device deletion.

Why it matters to the business

Kernel crashes or memory corruption on systems using mlxsw with GRE tunnels can lead to denial of service, potential privilege escalation, or data loss; widespread impact on Linux servers and network appliances running affected kernels.

How an attack unfolds

An attacker creates a GRE net device and adds a dummy neighbor entry, triggers a devlink reload to force incorrect offloading during replay, then deletes the neighbor and device; this leaves a dangling reference that is dereferenced during cleanup, resulting in use-after-free.

How to fix it

Update the Linux kernel to a version containing commit f1ecccb5cdda39bca8cd17bb0b6cf61361e33578 or later; for exfat-utils on Mageia 5 apply version 1.1.0-3.1.mga5 or newer; reboot after upgrade and verify mlxsw driver behavior with GRE devices.

How to confirm the fix worked

Confirm kernel build contains the fix commit; test by creating GRE device, adding neighbor, reloading devlink, and deleting the device while monitoring for KASAN or slab-use-after-free reports in dmesg.

Typical attack path

  1. Create GRE net device with ip link add type gre
  2. Add noarp neighbor entry on the GRE device
  3. Perform devlink dev reload on the mlxsw device
  4. Delete the neighbor and GRE net device to trigger use-after-free

How to detect it

Search kernel logs and dmesg for KASAN slab-use-after-free reports referencing mlxsw_sp_neigh_entry_update, mlxsw_sp_router_rif_gone_sync, or mlxsw_sp_netdevice_ipip_ol_event during GRE net device deletion events.

  • mlxsw_sp_neigh_entry_update+0x1ea/0x200
  • BUG: KASAN: slab-use-after-free
  • Read of size 8 at addr
  • mlxsw_sp_router_rif_gone_sync
  • mlxsw_sp_netdevice_ipip_ol_event

What your security team should do

  • Prioritize kernel upgrade on all systems exposing mlxsw or using GRE offload
  • Review and restrict unprivileged creation of GRE net devices via network namespaces or capabilities
  • Enable KASAN or similar memory debugging in test environments to validate the fix
  • Monitor changelogs for backports to distribution kernels and apply within maintenance windows

The record

In the Linux kernel, the following vulnerability has been resolved: mlxsw: spectrum_router: Fix use-after-free when deleting GRE net devices The driver only offloads neighbors that are constructed on top of net devices registered by it or their uppers (which are all Ethernet). The device supports GRE encapsulation and decapsulation of forwarded traffic, but the driver will not offload dummy neighbors constructed on top of GRE net devices as they are not uppers of its net devices: # ip link add name gre1 up type gre tos inherit local 192.0.2.1 remote 198.51.100.1 # ip neigh add 0.0.0.0 lladdr 0.0.0.0 nud noarp dev gre1 $ ip neigh show dev gre1 nud noarp 0.0.0.0 lladdr 0.0.0.0 NOARP (Note that the neighbor is not marked with 'offload') When the driver is reloaded and the existing configuration is replayed, the driver does not perform the same check regarding existing neighbors and offloads the previously added one: # devlink dev reload pci/0000:01:00.0 $ ip neigh show dev gre1 nud noarp 0.0.0.0 lladdr 0.0.0.0 offload NOARP If the neighbor is later deleted, the driver will ignore the notification (given the GRE net device is not its upper) and will therefore keep referencing freed memory, resulting in a use-after-free [1] when the net device is deleted: # ip neigh del 0.0.0.0 lladdr 0.0.0.0 dev gre1 # ip link del dev gre1 Fix by skipping neighbor replay if the net device for which the replay is performed is not our upper. [1] BUG: KASAN: slab-use-after-free in mlxsw_sp_neigh_entry_update+0x1ea/0x200 Read of size 8 at addr ffff888155b0e420 by task ip/2282 [...] Call Trace: <TASK> dump_stack_lvl+0x6f/0xa0 print_address_description.constprop.0+0x6f/0x350 print_report+0x108/0x205 kasan_report+0xdf/0x110 mlxsw_sp_neigh_entry_update+0x1ea/0x200 mlxsw_sp_router_rif_gone_sync+0x2a8/0x440 mlxsw_sp_rif_destroy+0x1e9/0x750 mlxsw_sp_netdevice_ipip_ol_event+0x3c9/0xdc0 mlxsw_sp_router_netdevice_event+0x3ac/0x15e0 notifier_call_chain+0xca/0x150 call_netdevice_notifiers_info+0x7f/0x100 unregister_netdevice_many_notify+0xc8c/0x1d90 rtnl_dellink+0x34e/0xa50 rtnetlink_rcv_msg+0x6fb/0xb70 netlink_rcv_skb+0x131/0x360 netlink_unicast+0x426/0x710 netlink_sendmsg+0x75a/0xc20 __sock_sendmsg+0xc1/0x150 ____sys_sendmsg+0x5aa/0x7b0 ___sys_sendmsg+0xfc/0x180 __sys_sendmsg+0x121/0x1b0 do_syscall_64+0xbb/0x1d0 entry_SYSCALL_64_after_hwframe+0x4b/0x53

Affected packages

Ecosystem Package Introduced Fixed
Debian:13 linux 0 6.12.30-1
Linux Kernel 6.6.0 6.6.92
openSUSE:Leap 16.0 dtb-aarch64 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-64kb 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-default 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-default-base 0 6.12.0-160000.6.1.160000.2.4
openSUSE:Leap 16.0 kernel-docs 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-kvmsmall 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-obs-build 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-obs-qa 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-rt 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-source 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-syms 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-zfcpdump 0 6.12.0-160000.6.1

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