CVE-2025-40039Network attack vector

Kernel memory compromise via RPC handle race

Published Oct 28, 2025 · Updated Oct 28, 2025

A race condition in Linux ksmbd allows remote authenticated users to read or write kernel memory or crash the SMB server. ksmbd_session_rpc_open() modifies sess->rpc_handle_list under a read lock, while ksmbd_session_rpc_method() loads and dereferences entries without any lock. A valid low-privileged SMB session and concurrent pipe-handle requests reach the flaw; guest mapping can remove the credential gate.

CVSS severity8.8
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A race condition in Linux ksmbd allows remote authenticated users to read or write kernel memory or crash the SMB server. ksmbd_session_rpc_open() modifies sess->rpc_handle_list under a read lock, while ksmbd_session_rpc_method() loads and dereferences entries without any lock. A valid low-privileged SMB session and concurrent pipe-handle requests reach the flaw; guest mapping can remove the credential gate.

The record

CVE
CVE-2025-40039
Published
Oct 28, 2025
Updated
Oct 28, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-362, T1210
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 28, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=052b41ef2abe274f068e892aee81406f11bd1f3a
  2. Affected versionversion=1f485b54d04a920723984062c912174330a05178
  3. Affected versionversion=6.3
  4. Affected versionversion=b685757c7b08d5073046fb379be965fd6c06aafc <305853cce379407090a73b38c5de5ba748893aee
  5. Affected versionversion=b685757c7b08d5073046fb379be965fd6c06aafc <5cc679ba0f4505936124cd4179ba66bb0a4bd9f3
  6. Affected versionversion=b685757c7b08d5073046fb379be965fd6c06aafc <6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=052b41ef2abe274f068e892aee81406f11bd1f3a; version=1f485b54d04a920723984062c912174330a05178; version=6.3; version=b685757c7b08d5073046fb379be965fd6c06aafc <305853cce379407090a73b38c5de5ba748893aee; version=b685757c7b08d5073046fb379be965fd6c06aafc <5cc679ba0f4505936124cd4179ba66bb0a4bd9f3; version=b685757c7b08d5073046fb379be965fd6c06aafc <6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1

Published CVSS scores

4.7NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
8.8kernel.orgCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1210Exploitation of Remote Services

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

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Your stack

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