CVE-2026-74521Network attack vector

Incorrect SMB session matching via truncated ClientGUID comparison

Published Aug 15, 2026 · Updated Aug 15, 2026

Improper ClientGUID comparison in Linux kernel ksmbd 5.15 through 7.1.7 allows remote authenticated users to cause incorrect SMB session matching. The SMB3 multichannel binding and FSCTL_VALIDATE_NEGOTIATE_INFO paths use strncmp on a fixed-size binary ClientGUID, so an embedded NUL ends comparison before all 16 bytes are checked. A reachable ksmbd SMB3 service and a valid session are required; distinct client identifiers can be treated as equal, but the published record specifies no further consequence.

CVSS severityUnavailable
Unscored
EPSS probability0.32%
Next 30 days · Sep 17, 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

Improper ClientGUID comparison in Linux kernel ksmbd 5.15 through 7.1.7 allows remote authenticated users to cause incorrect SMB session matching. The SMB3 multichannel binding and FSCTL_VALIDATE_NEGOTIATE_INFO paths use strncmp on a fixed-size binary ClientGUID, so an embedded NUL ends comparison before all 16 bytes are checked. A reachable ksmbd SMB3 service and a valid session are required; distinct client identifiers can be treated as equal, but the published record specifies no further consequence.

The record

CVE
CVE-2026-74521
Published
Aug 15, 2026
Updated
Aug 15, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1210
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 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 <d535363299822c5caa543787b21bd5cfa3e41949
  3. Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <e8bb506e6ef749ac0336f3e579d8d02396b7d832

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.15; version=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <d535363299822c5caa543787b21bd5cfa3e41949; version=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <e8bb506e6ef749ac0336f3e579d8d02396b7d832

Published CVSS scores

No CVSS assessment is available in this record.

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 11, 2026Sep 17, 2026
Latest reporting daySep 17, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1210Exploitation of Remote Services

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