CVE-2023-52440Network attack vector

Kernel code execution via oversized NTLMSSP session key

Published Feb 21, 2024 · Updated Aug 15, 2026

Heap-based buffer overflow in Linux ksmbd allows remote attackers to execute kernel code through crafted SMB session setup. The ksmbd_decode_ntlmssp_auth_blob() path passes an attacker-controlled SessionKey length to cifs_arc4_crypt(), which copies beyond the 40-byte sess_key buffer when the length exceeds CIFS_KEY_SIZE. Exploitation requires ksmbd to be enabled but needs no valid credentials or user interaction, and heap corruption can crash the host or permit kernel-level code execution.

CVSS severity9.8
Critical
EPSS probability21.91%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Linux ksmbd allows remote attackers to execute kernel code through crafted SMB session setup. The ksmbd_decode_ntlmssp_auth_blob() path passes an attacker-controlled SessionKey length to cifs_arc4_crypt(), which copies beyond the 40-byte sess_key buffer when the length exceeds CIFS_KEY_SIZE. Exploitation requires ksmbd to be enabled but needs no valid credentials or user interaction, and heap corruption can crash the host or permit kernel-level code execution.

The record

CVE
CVE-2023-52440
Published
Feb 21, 2024
Updated
Aug 15, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 21, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 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=5.17
  2. Affected versionversion=c5049d2d73b2dc8e6bb64be633250bad1ae3d9ef <bd554ed4fdc3d38404a1c43d428432577573e809
  3. Affected versionversion=f9929ef6a2a55f03aac61248c6a3a987b8546f2a <30fd6521b2fbd9b767e438e31945e5ea3e3a2fba
  4. Affected versionversion=f9929ef6a2a55f03aac61248c6a3a987b8546f2a <4b081ce0d830b684fdf967abc3696d1261387254
  5. Affected versionversion=f9929ef6a2a55f03aac61248c6a3a987b8546f2a <7f1d6cb0eb6af3a8088dc24b7ddee9a9711538c4
  6. Affected versionversion=f9929ef6a2a55f03aac61248c6a3a987b8546f2a <ecd7e1c562cb08e41957fcd4b0e404de5ab38e20

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.17; version=c5049d2d73b2dc8e6bb64be633250bad1ae3d9ef <bd554ed4fdc3d38404a1c43d428432577573e809; version=f9929ef6a2a55f03aac61248c6a3a987b8546f2a <30fd6521b2fbd9b767e438e31945e5ea3e3a2fba; version=f9929ef6a2a55f03aac61248c6a3a987b8546f2a <4b081ce0d830b684fdf967abc3696d1261387254; version=f9929ef6a2a55f03aac61248c6a3a987b8546f2a <7f1d6cb0eb6af3a8088dc24b7ddee9a9711538c4; version=f9929ef6a2a55f03aac61248c6a3a987b8546f2a <ecd7e1c562cb08e41957fcd4b0e404de5ab38e20

Published CVSS scores

9.8Linux kernel CVE teamCVSS: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

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

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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 exploitUnconfirmed

Weakness, pattern, technique

T1190Exploit Public-Facing Application

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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