CVE-2025-39850 Vulnerability Analysis & Exploit Details

CVE-2025-39850
Vulnerability Scoring

Analysis In Progress
Analysis In Progress

Attack Complexity Details

  • Attack Complexity:
    Attack Complexity Analysis In Progress
  • Attack Vector:
    Attack Vector Under Analysis
  • Privileges Required: None
    No authentication is required for exploitation.
  • Scope:
    Impact is confined to the initially vulnerable component.
  • User Interaction: None
    No user interaction is necessary for exploitation.

CVE-2025-39850 Details

Status: Awaiting Analysis

Last updated: 🕘 22 Sep 2025, 21:23 UTC
Originally published on: 🕓 19 Sep 2025, 16:15 UTC

Time between publication and last update: 3 days

CVSS Release:

CVE-2025-39850 Vulnerability Summary

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 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: <TASK> 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_xmit+0x803/0x1600 [...] Call Trace: <TASK> dev_hard_start_xmit+0x5d/0x1c0 __dev_queue_xmit+0x246/0xfd0 ip6_finish_output2+0x210/0x6c0 ip6_finish_output+0x1af/0x2b0 ip6_mr_output+0x92/0x3e0 ip6_send_skb+0x30/0x90 rawv6_sendmsg+0xe6e/0x12e0 __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 RIP: 0033:0x7f383422ec77 [4] #!/bin/bash ip address add 2001:db8:1::1/128 dev lo ip nexthop add id 1 via 2001:db8:1::1 fdb ip nexthop add id 10 group 1 fdb ip link add name vx0 up type vxlan id 10010 local 2001:db8:1::1 dstport 4789 proxy ip neigh add 2001:db8:1::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 ndisc6 -r 1 -s 2001:db8:1::1 -w 1 2001:db8:1::3 vx0

Assessing the Risk of CVE-2025-39850

Access Complexity Graph

The exploitability of CVE-2025-39850 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2025-39850

No exploitability data is available for CVE-2025-39850.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2025-39850, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2025-39850, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: None
    CVE-2025-39850 does not compromise confidentiality.
  • Integrity: None
    CVE-2025-39850 does not impact data integrity.
  • Availability: None
    CVE-2025-39850 does not affect system availability.

CVE-2025-39850 References

External References

CWE Common Weakness Enumeration

Unknown

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