CVE-2023-32255Network attack vector

Denial of service via leaked ksmbd sessions

Published Aug 2, 2025 · Updated Jun 29, 2026

Memory leak in Linux Kernel ksmbd allows remote attackers to exhaust memory via unauthenticated SMB2 session-setup requests. The smb2_sess_setup handler accepts an unknown NTLMSSP MessageType without returning an error, creating a session with no channel that ksmbd_sessions_deregister does not destroy. Exploitation requires ksmbd to be enabled; repeated malformed requests consume kernel memory and can deny service.

CVSS severity5.3
Medium
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in Linux Kernel ksmbd allows remote attackers to exhaust memory via unauthenticated SMB2 session-setup requests. The smb2_sess_setup handler accepts an unknown NTLMSSP MessageType without returning an error, creating a session with no channel that ksmbd_sessions_deregister does not destroy. Exploitation requires ksmbd to be enabled; repeated malformed requests consume kernel memory and can deny service.

The record

CVE
CVE-2023-32255
Published
Aug 2, 2025
Updated
Jun 29, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-772, T1499.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 2, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 29, 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=0 <5.15.111
  2. Affected versionversion=6.0.0 <6.0.*
  3. Affected versionversion=6.1.0 <6.1.28
  4. Affected versionversion=6.2.0 <6.2.15
  5. Affected versionversion=6.3.0 <6.3.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=0 <5.15.111; version=6.0.0 <6.0.*; version=6.1.0 <6.1.28; version=6.2.0 <6.2.15; version=6.3.0 <6.3.2

Published CVSS scores

5.3Red Hat, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-772Missing Release of Resource after Effective Lifetime
T1499.001OS Exhaustion Flood

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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