CVE-2023-32251Network attack vector

Accelerated credential guessing via asynchronous delay bypass

Published Jul 31, 2025 · Updated Jun 30, 2026

Improper authentication throttling in Linux Kernel ksmbd allows remote attackers to accelerate credential guessing over SMB. In smb2_sess_setup, a failed session setup sleeps for five seconds without blocking asynchronous work on the same connection. Only systems with ksmbd enabled are exposed; no authentication is required, and bypassing the delay permits faster dictionary attacks against configured SMB credentials.

CVSS severity3.7
Low
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication throttling in Linux Kernel ksmbd allows remote attackers to accelerate credential guessing over SMB. In smb2_sess_setup, a failed session setup sleeps for five seconds without blocking asynchronous work on the same connection. Only systems with ksmbd enabled are exposed; no authentication is required, and bypassing the delay permits faster dictionary attacks against configured SMB credentials.

The record

CVE
CVE-2023-32251
Published
Jul 31, 2025
Updated
Jun 30, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-307, T1110
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 31, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 30, 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 <5.15.145
  2. Affected versionversion=6.0.0 <6.0.*
  3. Affected versionversion=6.1.0 <6.1.29
  4. Affected versionversion=6.2.0 <6.2.16
  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 <5.15.145; version=6.0.0 <6.0.*; version=6.1.0 <6.1.29; version=6.2.0 <6.2.16; version=6.3.0 <6.3.2

Published CVSS scores

3.7Red HatCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

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-307Improper Restriction of Excessive Authentication Attempts
T1110Brute Force

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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