CVE-2026-64138: ksmbd: validate SID in parent security descriptor during ACL inheritance

criticalCVSS 9.8CVE-2026-64138

CSIRTS triage

Other

What: The ksmbd may not validate SID in the parent security descriptor during ACL inheritance.
Who is affected: Deployments using ksmbd.
Urgency: Remediation is high urgency due to the critical severity of the issue.
Action: Apply the patch for CVE-2026-64138.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: critical — CVSS 9.8
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64138

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-641380.41% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 34% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-64138	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for ksmbd

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-64437: In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free …nvd · 2026-07-25
highCVE-2026-64400: In the Linux kernel, the following vulnerability has been resolved: ksmbd: prevent path traver…nvd · 2026-07-25
criticalCVE-2026-64399: In the Linux kernel, the following vulnerability has been resolved: ksmbd: add permission chec…nvd · 2026-07-25
highCVE-2026-64398: In the Linux kernel, the following vulnerability has been resolved: ksmbd: add a permission ch…nvd · 2026-07-25
criticalCVE-2026-64397: In the Linux kernel, the following vulnerability has been resolved: ksmbd: serialize QUERY_DIR…nvd · 2026-07-25
highCVE-2026-64396: In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix UAF of struct f…nvd · 2026-07-25