CVE-2026-68388: smb/client: handle overlapping allocated ranges in fallocate

mediumCVSS 4.4CVE-2026-68388

CSIRTS triage

vendor: Linux product: Linux Kernel Denial of service

What: SMB client fallocate handler does not correctly handle overlapping allocated ranges, causing denial of service.
Who is affected: Systems using SMB client with fallocate support against malicious SMB servers.
Urgency: Medium severity; denial of service possible during file allocation operations.
Action: Update to a patched Linux kernel version when available.

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: medium — CVSS 4.4
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-68388

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-2026-683880.52% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 42% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-68388	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

unknownMultiple vulnerabilities in Red Hat Linux kernel (August 21, 2026)cert-fr-avis
unknownMultiple vulnerabilities in Debian LTS Linux kernel (August 21, 2026)cert-fr-avis
criticalCVE-2026-68388: In the Linux kernel, the following vulnerability has been resolved: smb/client: handle overlap…nvd

Recent advisories for smb/client

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.

mediumCVE-2026-64598: smb/client: Fix error code in smb2_aead_req_alloc()msrc · 2026-08-11
criticalCVE-2026-68388: In the Linux kernel, the following vulnerability has been resolved: smb/client: handle overlap…nvd · 2026-08-10
highCVE-2026-64598: In the Linux kernel, the following vulnerability has been resolved: smb/client: Fix error code…nvd · 2026-08-06
mediumCVE-2026-64388: smb/client: fix chown/chgrp with SMB3 POSIX Extensionsmsrc · 2026-08-06
highCVE-2026-64388: In the Linux kernel, the following vulnerability has been resolved: smb/client: fix chown/chgr…nvd · 2026-07-25
mediumCVE-2026-52967: smb/client: fix possible infinite loop and oob read in symlink_data()msrc · 2026-06-09