EUVD-2026-43907
GHSA-v4hp-j4fc-x9fp
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Local low-priv authenticated access (AV:L/PR:L/AC:L) with kernel memory disclosure gives C:H; description states only information disclosure so I:N and A:N, diverging from vendor's unexplained A:H.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Lifecycle Timeline
2DescriptionCVE.org
Out-of-bounds read in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to disclose information locally.
AnalysisAI
Local information disclosure in the Windows Container Isolation FS Filter Driver (unionfs.sys) on Windows 11 version 26H1 allows an authorized low-privileged user to read memory outside intended bounds and disclose sensitive kernel or process data. The flaw was reported by Microsoft, a vendor patch is available, and there is no public exploit identified at time of analysis. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to already be an authorized, low-privileged local user on a Windows 11 version 26H1 system (PR:L, AV:L) and to be able to invoke the Container Isolation filesystem path served by unionfs.sys - that is, the host must actually use container/isolation functionality (Windows containers, Windows Sandbox, or MSIX/AppX isolation) so the driver processes the attacker's filesystem operations. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H) describes a locally exploitable, low-complexity flaw requiring only low privileges and no user interaction, yielding high confidentiality impact - a credible priority for privilege-escalation-minded attackers who already have a foothold. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who already has a low-privileged local account or foothold on a Windows 11 26H1 host triggers crafted filesystem operations against an isolated/container volume so that unionfs.sys reads beyond an allocated buffer and returns adjacent kernel memory to user space. The leaked bytes (e.g., kernel pointers or credentials) are then used to bypass KASLR and chain into a privilege-escalation exploit. … |
| Remediation | Patch available per vendor advisory - apply the Microsoft security update for CVE-2026-50428 to Windows 11 version 26H1 as published at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50428 (consult the MSRC page for the exact KB number and build, which were not included in the provided data). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Windows 11 version 26H1 systems currently deployed, focusing on those hosting containerized workloads or supporting multiple concurrent users. …
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External POC / Exploit Code
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