CVE-2026-52944: ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE

criticalCVSS 9.8CVE-2026-52944

CSIRTS triage

product: ksmbd Authentication bypass

What: This vulnerability allows for a permission bypass in FSCTL_SET_SPARSE operations.
Who is affected: Deployments using ksmbd are affected.
Urgency: Remediation is critical due to the high severity rating of 9.8.
Action: Apply the patch for CVE-2026-52944.

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

⚡ Watch ksmbd

Get an email when a new ksmbd advisory drops — max one per day, one-click unsubscribe.

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: critical — CVSS 9.8
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-52944

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-2026-529440.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-52944	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

high[UPDATE] [high] Linux Kernel: Multiple vulnerabilitiescert-bund

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-2026-52996: ksmbd: fix durable fd leak on ClientGUID mismatch in durable v2 openmsrc · 2026-06-09
highCVE-2026-52911: ksmbd: scope conn->binding slowpath to bound sessions onlymsrc · 2026-06-09
highCVE-2026-53198: ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCELmsrc · 2026-06-09
criticalCVE-2026-53010: ksmbd: fix use-after-free in smb2_open during durable reconnectmsrc · 2026-06-09
mediumCVE-2026-53046: ksmbd: fix use-after-free from async crypto on Qualcomm crypto enginemsrc · 2026-06-09