CVE-2025-39838

Kernel crash via unchecked CIFS UTF-16 source

Published Sep 19, 2025 · Updated Sep 19, 2025

NULL pointer dereference in the Linux CIFS client allows local users to crash an affected kernel through an SFU node-creation path. The __cifs_sfu_make_node path passes a NULL source through cifs_strndup_to_utf16 into cifs_local_to_utf16_bytes, which dereferences it. Low-privileged local access to the affected CIFS path is required, and successful triggering interrupts the host by crashing its kernel.

CVSS severity5.5
Medium
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

NULL pointer dereference in the Linux CIFS client allows local users to crash an affected kernel through an SFU node-creation path. The __cifs_sfu_make_node path passes a NULL source through cifs_strndup_to_utf16 into cifs_local_to_utf16_bytes, which dereferences it. Low-privileged local access to the affected CIFS path is required, and successful triggering interrupts the host by crashing its kernel.

The record

CVE
CVE-2025-39838
Published
Sep 19, 2025
Updated
Sep 19, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499
Attack vector
local
Privileges
authenticated

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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1cfa5dd05847137f0fb3ce74ced80c0b4858d716
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1f797f062b5cf13a1c2bcc23285361baaa7c9260
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3c26a8d30ed6b53a52a023ec537dc50a6d34a67a
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <65b98a7e65e7a8f3894d8760cd194eaf20504c99
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <70bccd9855dae56942f2b18a08ba137bb54093a0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1cfa5dd05847137f0fb3ce74ced80c0b4858d716; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1f797f062b5cf13a1c2bcc23285361baaa7c9260; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3c26a8d30ed6b53a52a023ec537dc50a6d34a67a; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <65b98a7e65e7a8f3894d8760cd194eaf20504c99; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <70bccd9855dae56942f2b18a08ba137bb54093a0

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo