CVE-2026-23364Network attack vector

Authentication bypass via nonconstant NTLMv2 MAC comparison

Published Mar 25, 2026 · Updated Mar 25, 2026

Timing side channel in Linux Kernel ksmbd allows remote attackers to bypass SMB authentication with crafted NTLMv2 responses. The ksmbd_auth_ntlmv2, smb2_check_sign_req, and smb3_check_sign_req paths use memcmp, whose early return leaks how many MAC bytes match. Exploitation requires a reachable ksmbd SMB service and repeated timing measurements; successful MAC forgery grants read and write access to configured shares.

CVSS severity7.4
High
EPSS probability0.39%
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

Timing side channel in Linux Kernel ksmbd allows remote attackers to bypass SMB authentication with crafted NTLMv2 responses. The ksmbd_auth_ntlmv2, smb2_check_sign_req, and smb3_check_sign_req paths use memcmp, whose early return leaks how many MAC bytes match. Exploitation requires a reachable ksmbd SMB service and repeated timing measurements; successful MAC forgery grants read and write access to configured shares.

The record

CVE
CVE-2026-23364
Published
Mar 25, 2026
Updated
Mar 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 25, 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=5.15
  2. Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <2cdc56ed67615ba0921383a688f24415ebe065f3
  3. Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <307afccb751f542246bd5dc68a2c1ffe1a78418c
  4. Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <93c0a22fec914ec4b697e464895a0f594e29fb28
  5. Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <c5794709bc9105935dbedef8b9cf9c06f2b559fa
  6. Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <cd52a0e309659537048a864211abc3ea4c5caa63
  7. Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <f4588b85efd6007d46b80aa1b9fb746628ffb3dc

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5.15; version=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <2cdc56ed67615ba0921383a688f24415ebe065f3; version=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <307afccb751f542246bd5dc68a2c1ffe1a78418c; version=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <93c0a22fec914ec4b697e464895a0f594e29fb28; version=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <c5794709bc9105935dbedef8b9cf9c06f2b559fa; version=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <cd52a0e309659537048a864211abc3ea4c5caa63; version=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <f4588b85efd6007d46b80aa1b9fb746628ffb3dc

Published CVSS scores

7.4kernel.orgCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1190Exploit Public-Facing Application

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