CVE-2023-4515Network attack vector

Kernel disclosure and crash via short SMB2 requests

Published Aug 16, 2025 · Updated Aug 5, 2026

Out-of-bounds read in Linux ksmbd allows remote attackers to disclose kernel heap data or crash the host via crafted SMB2 requests. ksmbd_smb2_check_message fails to reject mismatched StructureSize2 values for most commands before handlers read fixed request fields beyond a short PDU. No valid SMB session or user interaction is required, but KSMBD must be running and reachable as an SMB server.

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

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds read in Linux ksmbd allows remote attackers to disclose kernel heap data or crash the host via crafted SMB2 requests. ksmbd_smb2_check_message fails to reject mismatched StructureSize2 values for most commands before handlers read fixed request fields beyond a short PDU. No valid SMB session or user interaction is required, but KSMBD must be running and reachable as an SMB server.

The record

CVE
CVE-2023-4515
Published
Aug 16, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2b9b8f3b68edb3d67d79962f02e26dbb5ae3808d <5aa4fda5aa9c2a5a7bac67b4a12b089ab81fee3c
  2. Affected versionversion=2b9b8f3b68edb3d67d79962f02e26dbb5ae3808d <ff7236b66d69582f90cf5616e63cfc3dc18142bb
  3. Affected versionversion=35f450f54dca1519bb24faacd0428db09f89a11f <595679098bdcdbfbba91ebe07a2f7f208df93870
  4. Affected versionversion=5.15.121 <5.15.127
  5. Affected versionversion=6.1.36 <6.1.46
  6. Affected versionversion=6.3.10 <6.4
  7. Affected versionversion=6.4
  8. Affected versionversion=768caf4019f0391c0b6452afe34cea1704133f7b
  9. Affected versionversion=9650cf70ec9d94ff34daa088b643229231723c26 <c6bef3bc30fd4a175aef846b7d928a6c40d091cd

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2b9b8f3b68edb3d67d79962f02e26dbb5ae3808d <5aa4fda5aa9c2a5a7bac67b4a12b089ab81fee3c; version=2b9b8f3b68edb3d67d79962f02e26dbb5ae3808d <ff7236b66d69582f90cf5616e63cfc3dc18142bb; version=35f450f54dca1519bb24faacd0428db09f89a11f <595679098bdcdbfbba91ebe07a2f7f208df93870; version=5.15.121 <5.15.127; version=6.1.36 <6.1.46; version=6.3.10 <6.4; version=6.4; version=768caf4019f0391c0b6452afe34cea1704133f7b; version=9650cf70ec9d94ff34daa088b643229231723c26 <c6bef3bc30fd4a175aef846b7d928a6c40d091cd

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
5.5UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/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

T1499.004Endpoint Denial of Service: Application or System Exploitation

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo