CVE-2026-64380: smb: client: harden POSIX SID length parsing

highCVSS 8.2CVE-2026-64380

CSIRTS triage

vendor: Linux product: smbOther

What: The smb client has been hardened against POSIX SID length parsing issues.
Who is affected: Deployments of the smb client are affected.
Urgency: Remediation is necessary to prevent potential exploitation, although exploitation status is currently unknown.
Action: Update to the latest version of the smb client.

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 8.2
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64380

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-2026-643800.44% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 36% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-64380	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

highCVE-2026-64380: In the Linux kernel, the following vulnerability has been resolved: smb: client: harden POSIX …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