CVE-2026-64389: ksmbd: validate NTLMv2 response before updating session key

highCVSS 7.8CVE-2026-64389

CSIRTS triage

vendor: Linux product: KSMBDOther

What: NTLMv2 responses are not validated before updating the session key.
Who is affected: Deployments using KSMBD.
Urgency: Remediation is important to prevent potential security issues, but no exploitation is reported.
Action: Update KSMBD to the latest version.

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

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.8
Published: 2026-08-06
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64389

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-2026-643890.45% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 38% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-64389	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

highCVE-2026-64389: In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate NTLMv2 res…nvd

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-2026-74522: In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free …nvd · 2026-08-15
criticalCVE-2026-74521: In the Linux kernel, the following vulnerability has been resolved: ksmbd: use memcmp() to com…nvd · 2026-08-15
unknownCVE-2026-74494: In the Linux kernel, the following vulnerability has been resolved: ksmbd: reject repeated SMB…nvd · 2026-08-15
highCVE-2026-72492: In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free …nvd · 2026-08-15
criticalCVE-2026-72422: In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free …nvd · 2026-08-15
highCVE-2026-72382: In the Linux kernel, the following vulnerability has been resolved: ksmbd: reject undersized D…nvd · 2026-08-15