CVE-2026-64387: smb: client: fix query directory replay double-free

mediumCVSS 5.5CVE-2026-64387

CSIRTS triage

Memory corruption

What: The vulnerability is a double-free issue in the SMB client when querying directories.
Who is affected: Deployments using the affected SMB client are at risk.
Urgency: Immediate remediation is advised due to the potential for exploitation leading to memory corruption.
Action: Apply the fix for the double-free issue in the SMB client.

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

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 5.5
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64387

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-2026-643870.46% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 37% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-64387	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

criticalCVE-2026-64387: In the Linux kernel, the following vulnerability has been resolved: smb: client: fix query dir…nvd

Recent advisories for smb

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.

criticalCVE-2026-39873: The issue was addressed with improved memory handling. This issue is fixed in macOS Sequoia 15…nvd · 2026-07-27
highCVE-2026-64448: In the Linux kernel, the following vulnerability has been resolved: smb: client: restrict impl…nvd · 2026-07-25
highCVE-2026-64402: In the Linux kernel, the following vulnerability has been resolved: coresight: ultrasoc-smb: F…nvd · 2026-07-25
highCVE-2026-64401: In the Linux kernel, the following vulnerability has been resolved: smb: client: resolve SWN t…nvd · 2026-07-25
criticalCVE-2026-64387: In the Linux kernel, the following vulnerability has been resolved: smb: client: fix query dir…nvd · 2026-07-25
criticalCVE-2026-64386: In the Linux kernel, the following vulnerability has been resolved: smb: client: fix query_inf…nvd · 2026-07-25