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Linux KernelOperating system · Linux

CVE-2023-4458

HIGH · 7.5 CVSS v3.1 Published 2024-11-14
Fix available
A fix is available. Upgrade to 6.6 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A flaw was found within the parsing of extended attributes in the kernel ksmbd module. The issue results from the lack of proper validation of user-supplied data, which can result in a read past the end of an allocated buffer. An attacker can leverage this to disclose sensitive information on affected installations of Linux. Only systems with ksmbd enabled are vulnerable to this CVE.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A buffer over-read vulnerability exists in the Linux kernel's ksmbd (SMB kernel server) module when parsing extended attributes. Due to insufficient validation of user-supplied data, an attacker can read past the end of an allocated buffer, potentially exposing sensitive information from kernel memory.

MitigationDisable the ksmbd module if SMB file serving is not required; otherwise, apply available kernel security updates that address this vulnerability and restart the ksmbd service.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:< 6.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify if ksmbd module is loaded
    Run 'lsmod | grep ksmbd' or check /proc/modules for ksmbd entry
    Affected if The ksmbd module appears in the loaded modules list, indicating the SMB kernel server is active
  2. Check the running kernel version
    Run 'uname -r' or check /proc/version to obtain the kernel version number
    Affected if The kernel version is earlier than 6.6 (for example, 5.x or 6.x versions below 6.6)
  3. Confirm ksmbd service or daemon status
    Run 'ps aux | grep ksmbd' or check systemd service status if applicable
    Affected if A ksmbd-related process is running, indicating SMB file serving is active
  4. Verify SMB shares are configured or active
    Check /etc/ksmbd/ or run 'smbstatus' if available, or look for SMB-related mounts
    Affected if SMB shares are exported or the system is serving files via SMB protocol
  5. Check if extended attributes are used on SMB shares
    Review SMB share configuration for 'ea support' or 'store dos attributes' options; check if applications use setfattr or getfattr on SMB-mounted paths
    Affected if Extended attribute support is enabled on any SMB share, as this is the attack vector

The environment is affected if ksmbd is loaded and serving SMB shares on a kernel version earlier than 6.6, with extended attributes in use on those shares.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.6 or later
Fixed in 6.6
Interim mitigation

Disable the ksmbd module if SMB file serving is not required; otherwise, apply available kernel security updates that address this vulnerability and restart the ksmbd service.

Recommended fix Moderate confidence

Linux Kernel 6.6 or later (e.g., 6.6.x stable branch)

  1. Identify the current Linux kernel version (e.g., `uname -r` or `cat /proc/version`)
  2. Verify if ksmbd is enabled on the system by checking if the ksmbd module is loaded (`lsmod | grep ksmbd`) or if it's compiled into the kernel
  3. Update the Linux kernel to version 6.6 or later using the distribution's package manager (e.g., `apt-get dist-upgrade`, `yum update`, or `dnf upgrade`)
  4. Reboot the system to load the new kernel
  5. After reboot, verify the new kernel version is running (`uname -r`) and confirm it is version 6.6 or later
  6. If ksmbd is not needed, consider disabling it to reduce attack surface by adding `ksmbd` to the system's blocklist or blacklist
Caveat Kernel upgrades may require updating out-of-tree kernel modules or drivers; verify compatibility with the new kernel version before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-4458 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data