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Vulnerabilities

Vulnerability · 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 is enabled on a VXLAN

Published Sep 19, 2025 · catalog updated Oct 14, 2026 · In the Linux kernel,

Check if you run it

No confirmed exploitation is on record for CVE-2025-39850. EPSS is 0.15%. Act only if a listed version of In the Linux kernel, is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (In the Linux kernel,).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.15%
Remediation
Advisory link
Affected products
Ubuntu:16.04:LTS linux-hwe-edge · Ubuntu:18.04:LTS linux-aws-5.0 · Ubuntu:18.04:LTS linux-aws-5.3 · Ubuntu:18.04:LTS linux-azure · Ubuntu:18.04:LTS linux-azure-5.3 · Ubuntu:18.04:LTS linux-azure-edge

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 RIP: 0010:vxlan

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Ubuntu:16.04:LTS linux-hwe-edge4.8.0-28.30~16.04.1, 4.8.0-30.32~16.04.1, 4.8.0-32.34~16.04.1
  • Ubuntu:18.04:LTS linux-aws-5.05.0.0-1021.24~18.04.1, 5.0.0-1022.25~18.04.1, 5.0.0-1023.26~18.04.1
  • Ubuntu:18.04:LTS linux-aws-5.35.3.0-1016.17~18.04.1, 5.3.0-1017.18~18.04.1, 5.3.0-1019.21~18.04.1
  • Ubuntu:18.04:LTS linux-azure4.15.0-1002.2, 4.15.0-1003.3, 4.15.0-1004.4
  • Ubuntu:18.04:LTS linux-azure-5.35.3.0-1007.8~18.04.1, 5.3.0-1008.9~18.04.1, 5.3.0-1009.10~18.04.1
  • Ubuntu:18.04:LTS linux-azure-edge4.18.0-1006.6~18.04.1, 4.18.0-1007.7~18.04.1, 4.18.0-1008.8~18.04.1
  • Ubuntu:18.04:LTS linux-gcp4.15.0-1001.1, 4.15.0-1003.3, 4.15.0-1005.5
  • Ubuntu:18.04:LTS linux-gcp-5.35.3.0-1008.9~18.04.1, 5.3.0-1009.10~18.04.1, 5.3.0-1010.11~18.04.1
  • Ubuntu:18.04:LTS linux-gke-4.154.15.0-1030.32, 4.15.0-1032.34, 4.15.0-1033.35
  • Ubuntu:18.04:LTS linux-gke-5.45.4.0-1025.25~18.04.1, 5.4.0-1027.28~18.04.1, 5.4.0-1029.31~18.04.1
  • Ubuntu:18.04:LTS linux-gkeop-5.45.4.0-1001.1, 5.4.0-1003.3, 5.4.0-1004.5
  • Ubuntu:18.04:LTS linux-hwe4.18.0-13.14~18.04.1, 4.18.0-14.15~18.04.1, 4.18.0-15.16~18.04.1

How to fix CVE-2025-39850

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-39850. EPSS is 0.15%. Act only if a listed version of In the Linux kernel, is installed.

Which versions are affected?

Compare what you have installed with 4.8.0-28.30~16.04.1, 4.8.0-30.32~16.04.1, 4.8.0-32.34~16.04.1, 5.0.0-1021.24~18.04.1, 5.0.0-1022.25~18.04.1, 5.0.0-1023.26~18.04.1, 5.3.0-1016.17~18.04.1, 5.3.0-1017.18~18.04.1, 5.3.0-1019.21~18.04.1, 4.15.0-1002.2, 4.15.0-1003.3, 4.15.0-1004.4, 5.3.0-1007.8~18.04.1, 5.3.0-1008.9~18.04.1, 5.3.0-1009.10~18.04.1, 4.18.0-1006.6~18.04.1, 4.18.0-1007.7~18.04.1, 4.18.0-1008.8~18.04.1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.15%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Ubuntu security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 19, 2025 · OpenSSF OSV / OSV Scanner

    Detected

    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

  2. Oct 14, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    linux-aws-6.8 fixed in 6.8.0-1050.53~22.04.1; linux-azure-6.8 fixed in 6.8.0-1051.57~22.04.1; linux-azure-fde-6.8 fixed in 6.8.0-1058.65~22.04.1; linux-gcp-6.8 fixed in 6.8.0-1052.55~22.04.1

  3. Oct 14, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    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

Sources

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.