CVE-2025-40320Network attack vector

Kernel compromise via stale SMB directory pointer

Published Dec 8, 2025 · Updated Aug 5, 2026

Use-after-free in the SMB client of affected Linux kernels allows remote attackers controlling an SMB server to corrupt kernel memory. On a retry in smb2_query_info_compound(), the first attempt can free cfid, but replay leaves that stale pointer for later cleanup to dereference. A CIFS mount to a malicious or compromised server, or an unsigned session exposed to an on-path attacker, is required; exploitation can disclose kernel memory, crash the host, or enable kernel-level code execution.

CVSS severity9.8
Critical
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the SMB client of affected Linux kernels allows remote attackers controlling an SMB server to corrupt kernel memory. On a retry in smb2_query_info_compound(), the first attempt can free cfid, but replay leaves that stale pointer for later cleanup to dereference. A CIFS mount to a malicious or compromised server, or an unsigned session exposed to an on-path attacker, is required; exploitation can disclose kernel memory, crash the host, or enable kernel-level code execution.

The record

CVE
CVE-2025-40320
Published
Dec 8, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 8, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record 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=433042a91f9373241307725b52de573933ffedbf <939c4e33005e2a56ea8fcedddf0da92df864bd3b
  2. Affected versionversion=4f1fffa2376922f3d1d506e49c0fd445b023a28e <327f89c21601ebb7889f8c97754b76f08ce95a0c
  3. Affected versionversion=4f1fffa2376922f3d1d506e49c0fd445b023a28e <5c76f9961c170552c1d07c830b5e145475151600
  4. Affected versionversion=4f1fffa2376922f3d1d506e49c0fd445b023a28e <b556c278d43f4707a9073ca74d55581b4f279806
  5. Affected versionversion=6.6.32 <6.6.117
  6. Affected versionversion=6.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=433042a91f9373241307725b52de573933ffedbf <939c4e33005e2a56ea8fcedddf0da92df864bd3b; version=4f1fffa2376922f3d1d506e49c0fd445b023a28e <327f89c21601ebb7889f8c97754b76f08ce95a0c; version=4f1fffa2376922f3d1d506e49c0fd445b023a28e <5c76f9961c170552c1d07c830b5e145475151600; version=4f1fffa2376922f3d1d506e49c0fd445b023a28e <b556c278d43f4707a9073ca74d55581b4f279806; version=6.6.32 <6.6.117; version=6.8

Published CVSS scores

9.8LinuxCVSS:3.1/AV:N/AC:L/PR:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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