Vulnary
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Critical· 9.1official fix available

CVE-2023-54203

CVE-2023-54203 is a critical kernel vulnerability in Linux's SMB server implementation (ksmbd) that causes memory corruption when handling old SMB1 requests. The flaw occurs when the system improperly processes SMB1 negotiations using SMB2 code, leading to out-of-bounds memory access. A fix has been released in updated kernel versions.

publishedDec 30, 2025
last modifiedAug 4, 2026
sourcesNVD
severity · cvss
9.1
critical · how bad it is
exploitation · epss
<1%
7th percentile · chance of exploitation in 30 days
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
auto-deletes from the system
counting…on Sep 3, 2026

An official fix is available, so this entry is kept for 30 days and then removed automatically.

01

Who is affected

Systems using vulnerable Linux kernel versions with the ksmbd SMB server component

02

Real-world impact

Could allow attackers to execute arbitrary code or crash the system via crafted SMB1 requests

03

Why this severity

CVSS 9.1 (critical) - High confidence in exploitability and severe impact

04

What to do about it

official fix available
recommended steps
  1. 011. Check your Linux kernel version against the affected range (pre-patched versions).
  2. 022. Apply the latest Linux kernel security update from your distribution's repository.
  3. 033. Reboot the system after applying the update to ensure the fix is active.

NVD vulnerability description and kernel patch notes

05

Timeline

  1. Dec 30, 2025 · Dec 30, 2025
    Published
    Disclosed and added to the National Vulnerability Database.
  2. Aug 4, 2026 · 1d ago
    Advisory updated
    The NVD record was last revised.
  3. Aug 4, 2026 · 1d ago
    Official fix available
    A vendor patch or mitigation now exists — see the remediation steps above.
06

How it’s attacked

Attack vectorNetwork (remote)
Attack complexityLow
Privileges requiredNone
User interactionNone needed
ScopeUnchanged
Confidentiality impactHigh
Integrity impactNone
Availability impactHigh
07

References & advisories

NVD advisory ↗Search advisories ↗
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →