CVE-2025-39851Public exploitNetwork attack vector

Remote kernel crash via VXLAN FDB refresh

Published Sep 19, 2025 · Updated Sep 19, 2025

NULL pointer dereference in Linux kernel VXLAN allows remote attackers to crash the host with a crafted VXLAN packet. The vxlan_snoop path refreshes an FDB nexthop-group entry by dereferencing a remote destination that the entry does not contain. A routable VXLAN datagram with a matching inner source MAC reaches the fault when learning and a nexthop-backed FDB entry are enabled, causing a deterministic kernel crash.

CVSS severity7.5
High
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Linux kernel VXLAN allows remote attackers to crash the host with a crafted VXLAN packet. The vxlan_snoop path refreshes an FDB nexthop-group entry by dereferencing a remote destination that the entry does not contain. A routable VXLAN datagram with a matching inner source MAC reaches the fault when learning and a nexthop-backed FDB entry are enabled, causing a deterministic kernel crash.

The record

CVE
CVE-2025-39851
Published
Sep 19, 2025
Updated
Sep 19, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 19, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 19, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1274e1cc42264d4e629841e4f182795cb0becfd2 <0e8630f24c14d9c655d19eabe2e52a9e9f713307
  2. Affected versionversion=1274e1cc42264d4e629841e4f182795cb0becfd2 <4ff4f3104da6507e0f118c63c4560dfdeb59dce3
  3. Affected versionversion=1274e1cc42264d4e629841e4f182795cb0becfd2 <6ead38147ebb813f08be6ea8ef547a0e4c09559a
  4. Affected versionversion=5.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1274e1cc42264d4e629841e4f182795cb0becfd2 <0e8630f24c14d9c655d19eabe2e52a9e9f713307; version=1274e1cc42264d4e629841e4f182795cb0becfd2 <4ff4f3104da6507e0f118c63c4560dfdeb59dce3; version=1274e1cc42264d4e629841e4f182795cb0becfd2 <6ead38147ebb813f08be6ea8ef547a0e4c09559a; version=5.8

Published CVSS scores

5.5CISA ADP VulnrichmentCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.5LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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