cbcvebase.
CVE-2025-39850
published 2025-09-19

CVE-2025-39850: In the Linux kernel, the following vulnerability has been resolved: vxlan: Fix NPD in {arp,neigh}_reduce() when using nexthop objects When the "proxy" option…

PriorityP422medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
EPSS
0.14%
3.4th percentile
In the Linux kernel, the following vulnerability has been resolved: vxlan: Fix NPD in {arp,neigh}_reduce() when using nexthop objects When the "proxy" option is enabled on a VXLAN device, the device will suppress ARP requests and IPv6 Neighbor Solicitation messages if it is able to reply on behalf of the remote host. That is, if a matching and valid neighbor entry is configured on the VXLAN device whose MAC address is not behind the "any" remote (0.0.0.0 / ::). The code currently assumes that the FDB entry for the neighbor's MAC address points to a valid remote destination, but this is incorrect if the entry is associated with an FDB nexthop group. This can result in a NPD [1][3] which can be reproduced using [2][4]. Fix by checking that the remote destination exists before dereferencing it. [1] BUG: kernel NULL pointer dereference, address: 0000000000000000 [...] CPU: 4 UID: 0 PID: 365 Comm: arping Not tainted 6.17.0-rc2-virtme-g2a89cb21162c #2 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014 RIP: 0010:vxlan_xmit+0xb58/0x15f0 [...] Call Trace: dev_hard_start_xmit+0x5d/0x1c0 __dev_queue_xmit+0x246/0xfd0 packet_sendmsg+0x113a/0x1850 __sock_sendmsg+0x38/0x70 __sys_sendto+0x126/0x180 __x64_sys_sendto+0x24/0x30 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x4b/0x53 [2] #!/bin/bash ip address add 192.0.2.1/32 dev lo ip nexthop add id 1 via 192.0.2.2 fdb ip nexthop add id 10 group 1 fdb ip link add name vx0 up type vxlan id 10010 local 192.0.2.1 dstport 4789 proxy ip neigh add 192.0.2.3 lladdr 00:11:22:33:44:55 nud perm dev vx0 bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10 arping -b -c 1 -s 192.0.2.1 -I vx0 192.0.2.3 [3] BUG: kernel NULL pointer dereference, address: 0000000000000000 [...] CPU: 13 UID: 0 PID: 372 Comm: ndisc6 Not tainted 6.17.0-rc2-virtmne-g6ee90cb26014 #3 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1v996), BIOS 1.17.0-4.fc41 04/01/2x014 R

Affected

24 ranges
VendorProductVersion rangeFixed in
debianlinux< linux 6.16.6-1 (forky)linux 6.16.6-1 (forky)
linuxlinux
linuxlinux>= 1274e1cc42264d4e629841e4f182795cb0becfd2 < e211e3f4199ac829bd493632efcd131d337cba9de211e3f4199ac829bd493632efcd131d337cba9d
linuxlinux>= 1274e1cc42264d4e629841e4f182795cb0becfd2 < 8cfa0f076842f9b3b4eb52ae0e41d16e25cbf8fa8cfa0f076842f9b3b4eb52ae0e41d16e25cbf8fa
linuxlinux>= 1274e1cc42264d4e629841e4f182795cb0becfd2 < 1f5d2fd1ca04a23c18b1bde9a43ce2fa2ffa1bce1f5d2fd1ca04a23c18b1bde9a43ce2fa2ffa1bce
linuxlinux_kernel
linuxlinux_kernel>= 0 < 6.12.48-16.12.48-1
linuxlinux_kernel>= 0 < 6.16.6-16.16.6-1
linuxlinux_kernel>= 0 < 6.8.0-106.1066.8.0-106.106
linuxlinux_kernel>= 5.8 < 6.12.466.12.46
linuxlinux_kernel>= 6.13 < 6.16.66.16.6
msrcazl3_kernel_6.6.104.2-4_on_azure_linux_3.0
msrcazl3_kernel_6.6.112.1-2_on_azure_linux_3.0
msrcazl3_kernel_6.6.117.1-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.119.3-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.119.3-3_on_azure_linux_3.0
msrcazl3_kernel_6.6.121.1-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.126.1-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.130.1-3_on_azure_linux_3.0
msrcazl3_kernel_6.6.96.2-2_on_azure_linux_3.0
msrccbl2_kernel_5.15.186.1-1_on_cbl_mariner_2.0
msrccbl2_kernel_5.15.200.1-1_on_cbl_mariner_2.0
msrccbl2_kernel_5.15.202.1-1_on_cbl_mariner_2.0
ubuntulinux-xilinx

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
osv5.5MEDIUM
vendor_ubuntu7.8HIGH
vendor_msrc7.0HIGH
vendor_debian5.5MEDIUM
vendor_redhat5.5MEDIUM
Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.