CVE-2023-54203Network attack vector

Kernel memory disclosure via SMB1 negotiation mismatch

Published Dec 30, 2025 · Updated Dec 30, 2025

Out-of-bounds read in Linux ksmbd allows remote attackers to disclose kernel memory through a crafted pre-authentication SMB1 negotiate request. init_smb2_rsp_hdr treats the 56-byte SMB1 negotiate buffer as an SMB2 request and copies 16 bytes beyond its end into the response signature. The request reaches TCP port 445 before authentication when ksmbd is enabled; each response exposes 16 adjacent kernel bytes, and guarded or panic-on-warning builds crash.

CVSS severity9.1
Critical
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Linux ksmbd allows remote attackers to disclose kernel memory through a crafted pre-authentication SMB1 negotiate request. init_smb2_rsp_hdr treats the 56-byte SMB1 negotiate buffer as an SMB2 request and copies 16 bytes beyond its end into the response signature. The request reaches TCP port 445 before authentication when ksmbd is enabled; each response exposes 16 adjacent kernel bytes, and guarded or panic-on-warning builds crash.

The record

CVE
CVE-2023-54203
Published
Dec 30, 2025
Updated
Dec 30, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 30, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 30, 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=0b3ec5671ac06829ccebdaeec05acedfec327f42 <a8334a0c535d0f0b4d64926c8fe0922ed98f7d43
  2. Affected versionversion=39b291b86b5988bf8753c3874d5c773399d09b96 <dc8289f912387c3bcfbc5d2db29c8947fa207c11
  3. Affected versionversion=5.15.105 <5.15.145
  4. Affected versionversion=51a8534c0f35c0401e45f1055f914729cad98bf9 <921536046bd165efeb07beef5630aff35cd6a489
  5. Affected versionversion=6.1.22 <6.1.24
  6. Affected versionversion=6.2.9 <6.2.11
  7. Affected versionversion=cc32cd98a0aee4cc3eb611cbce11795b1aaa738a <99a51c673b1d2d0b5a972353401b77612d9cc713

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0b3ec5671ac06829ccebdaeec05acedfec327f42 <a8334a0c535d0f0b4d64926c8fe0922ed98f7d43; version=39b291b86b5988bf8753c3874d5c773399d09b96 <dc8289f912387c3bcfbc5d2db29c8947fa207c11; version=5.15.105 <5.15.145; version=51a8534c0f35c0401e45f1055f914729cad98bf9 <921536046bd165efeb07beef5630aff35cd6a489; version=6.1.22 <6.1.24; version=6.2.9 <6.2.11; version=cc32cd98a0aee4cc3eb611cbce11795b1aaa738a <99a51c673b1d2d0b5a972353401b77612d9cc713

Published CVSS scores

9.1Linux kernel CVE teamCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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.

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

No sourced classifications are available.

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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