CVE-2026-62770 Overview
CVE-2026-62770 is a heap-based buffer overflow [CWE-122] in Microsoft Windows Shell. An authorized local attacker can trigger the overflow to elevate privileges on affected systems. The flaw impacts a broad range of Windows client and server releases, including Windows 10, Windows 11, and Windows Server versions from 2012 through 2025.
Successful exploitation yields high impact to confidentiality, integrity, and availability. Because the attack vector is local and requires low privileges with no user interaction, it is well suited for post-compromise elevation by malware or an interactive attacker.
Critical Impact
Local privilege escalation to SYSTEM through a Windows Shell heap corruption, affecting nearly every supported Windows release.
Affected Products
- Microsoft Windows 10 (1607, 1809, 21H2, 22H2) on x86, x64, and ARM64
- Microsoft Windows 11 (23H2, 24H2, 25H2, 26H1) on x64 and ARM64
- Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025
Discovery Timeline
- 2026-08-11 - CVE-2026-62770 published to NVD
- 2026-08-13 - Last updated in NVD database
Technical Details for CVE-2026-62770
Vulnerability Analysis
The vulnerability is a heap-based buffer overflow in the Windows Shell, the component that powers Explorer, the taskbar, common shell dialogs, and shell extension handlers. An authenticated local user can supply crafted input that Windows Shell copies into a heap buffer without adequate bounds checking. The out-of-bounds write corrupts adjacent heap metadata or object fields.
By shaping the heap and controlling the overflowed data, an attacker can influence function pointers, virtual table references, or IPC state used by shell components running with higher privileges. Because Windows Shell interacts with brokered services and privileged handlers, a successful primitive can be leveraged to execute code in a SYSTEM context.
Root Cause
The root cause is missing or incorrect size validation on a heap allocation path inside Windows Shell code, categorized as [CWE-122]. Microsoft's advisory does not disclose the specific parsing routine or shell interface responsible. Refer to the Microsoft CVE-2026-62770 Advisory for authoritative technical details.
Attack Vector
Exploitation requires local access and a low-privileged account on the target host. The attacker interacts with a Windows Shell surface, such as a shell object, extension, or IPC endpoint, that processes attacker-controlled data. No user interaction is required beyond the attacker's own session, which makes the flaw suitable as a second-stage escalation after initial access from phishing, malicious documents, or a compromised standard user account.
No public proof-of-concept or exploit is currently listed in the enriched data, and the CVE is not present on the CISA Known Exploited Vulnerabilities catalog. The EPSS probability is 0.246%.
Detection Methods for CVE-2026-62770
Indicators of Compromise
- Unexpected crashes or Windows Error Reporting entries referencing explorer.exe, shell32.dll, or related shell components on patched-but-unpatched hosts.
- Standard user processes spawning child processes running as SYSTEM without a legitimate elevation path such as consent.exe (UAC).
- New scheduled tasks, services, or drivers created shortly after anomalous shell process activity.
Detection Strategies
- Hunt for process lineage where a shell-hosted process launches administrative binaries (cmd.exe, powershell.exe, reg.exe) with an integrity level jump to High or System.
- Alert on shell processes loading unsigned or unusual DLLs from user-writable paths, a common staging step for shell-based escalation.
- Correlate application crash telemetry from shell binaries with subsequent privileged process creation events on the same host.
Monitoring Recommendations
- Ingest Windows Security, Sysmon, and WER telemetry into a centralized data lake to enable cross-event correlation of shell crashes and privilege transitions.
- Track token elevation events (Event ID 4672) that occur outside of expected administrative workflows.
- Monitor Microsoft patch compliance for the August 2026 update cycle across all Windows 10, Windows 11, and Windows Server endpoints.
How to Mitigate CVE-2026-62770
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2026-62770 Advisory to all affected Windows client and server systems.
- Prioritize multi-user systems, jump hosts, RDS/VDI servers, and developer workstations where local access by non-administrators is common.
- Audit local account membership and remove unnecessary interactive logon rights on servers.
Patch Information
Microsoft has released updates for all listed affected products through the standard Windows Update and Microsoft Update Catalog channels. Consult the Microsoft CVE-2026-62770 Advisory for KB article numbers and per-SKU package identifiers.
Workarounds
- No vendor-supplied workaround is documented. Apply the security update as the primary remediation.
- Reduce exposure by enforcing least privilege, restricting interactive logon, and requiring Windows Defender Application Control or AppLocker policies that block untrusted binaries in user-writable locations.
- Enable attack surface reduction rules and exploit protection settings that harden heap allocators against corruption primitives.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
