EUVD-2026-56346
GHSA-8mmc-mc95-2ph5
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local attack vector, low complexity, and low-privileged account suffice; full C/I/A impact reflects SYSTEM-level privilege escalation within the unchanged host scope.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Integer underflow (wrap or wraparound) in Windows Program Compatibility Assistant Service allows an authorized attacker to elevate privileges locally.
AnalysisAI
Privilege escalation in the Windows Program Compatibility Assistant (PCA) Service, affecting a broad range of Windows 10, Windows 11, and Windows Server releases, stems from an integer underflow (CWE-191) that an authenticated local attacker can trigger to gain elevated - likely SYSTEM-level - privileges. The vulnerability requires only low-privileged local access with no user interaction, producing total confidentiality, integrity, and availability impact per the CVSS vector. SSVC assessment confirms no exploitation activity at time of analysis and no public exploit code has been identified.
Technical ContextAI
The Windows Program Compatibility Assistant Service is a built-in Windows component responsible for detecting and flagging application compatibility issues at runtime. CWE-191 (Integer Underflow / Wraparound) describes a condition where arithmetic produces a value below the minimum representable integer for the data type, causing the result to wrap around to a very large positive value. In a privileged service context, such a wraparound can corrupt size calculations for memory allocations or buffer boundaries, enabling an attacker to write beyond intended memory regions or otherwise influence control flow within a SYSTEM-privileged process. The affected product surface spans Windows 10 (versions 1607 through 22H2), Windows 11 (versions 23H2 through 26H1), and Windows Server editions from 2016 through 2025, as confirmed by ENISA EUVD-2026-56346 CPE data.
RemediationAI
Apply the Microsoft-released patches for each affected Windows version as documented in the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62696. Target build thresholds confirmed by ENISA EUVD-2026-56346 are: Windows 10 1607 / Server 2016 → 10.0.14393.9418 or later; Windows 10 1809 / Server 2019 → 10.0.17763.9115 or later; Windows 10 21H2 → 10.0.19044.7663 or later; Windows 10 22H2 → 10.0.19045.7663 or later; Windows 11 23H2 → 10.0.22631.7517 or later; Windows 11 24H2 and Server 2025 → 10.0.26100.9168 (client) / 10.0.26100.33296 (server) or later; Windows 11 25H2 → 10.0.26200.9168 or later; Windows 11 26H1 → 10.0.28000.2704 or later; Windows Server 2022 → 10.0.20348.5499 or later. If immediate patching is not feasible, limit interactive or remote login access for untrusted accounts on affected hosts, as the attack requires an authenticated local session. Disabling the Program Compatibility Assistant Service (PcaSvc) via Group Policy is a potential workaround but may break application compatibility detection and should be tested before deployment. Prioritize patching on multi-user systems, terminal servers, and developer workstations where low-privileged account access is common.
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Same weakness CWE-191 – Integer Underflow
View allSame technique Information Disclosure
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External POC / Exploit Code
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