CVE-2026-49183 Overview
CVE-2026-49183 is a race condition vulnerability in the Windows Clipboard Server that enables local privilege escalation. The flaw stems from concurrent execution using a shared resource with improper synchronization [CWE-362]. An authorized local attacker who wins the race can elevate privileges on the affected host. Microsoft assigned the issue a CVSS 3.1 base score of 7.0 and rates it HIGH severity. The vulnerability affects a broad range of currently supported Windows client and server releases, including Windows 10, Windows 11, and Windows Server 2019 through 2025.
Critical Impact
A successful exploit grants an authorized local attacker high impact to confidentiality, integrity, and availability through privilege elevation on the affected Windows host.
Affected Products
- Microsoft Windows 10 (1809, 21H2, 22H2) on x86, x64, and ARM64
- Microsoft Windows 11 (24H2, 25H2, 26H1) on x64 and ARM64
- Microsoft Windows Server 2019, 2022, and 2025
Discovery Timeline
- 2026-07-14 - CVE-2026-49183 published to the National Vulnerability Database
- 2026-07-20 - Last updated in NVD database
Technical Details for CVE-2026-49183
Vulnerability Analysis
The vulnerability resides in the Windows Clipboard Server, a system component that mediates clipboard operations between user sessions and privileged services. The flaw is classified as a race condition [CWE-362] in which two or more execution paths access a shared clipboard resource without adequate synchronization. An attacker with valid local credentials can trigger overlapping operations to reach a state the developers did not anticipate. Winning that race yields code execution or state manipulation in a higher-privileged context. The result is elevation of privilege on the local machine, allowing the attacker to break out of a standard user context.
Root Cause
The root cause is improper synchronization when multiple threads or processes concurrently access a shared clipboard object inside the Clipboard Server. Without correct locking, the window between validation and use can be manipulated to substitute or modify the resource. This is a classic time-of-check to time-of-use pattern captured by [CWE-362].
Attack Vector
Exploitation requires local access and low privileges but no user interaction. Attack complexity is high because the attacker must reliably win the timing race against the Clipboard Server. A successful attacker gains high impact to confidentiality, integrity, and availability. The vulnerability is not listed on the CISA Known Exploited Vulnerabilities catalog, and no public proof-of-concept exploit is currently available. The EPSS probability is 0.156%.
No verified public exploit code is available for CVE-2026-49183. See the Microsoft CVE-2026-49183 Advisory for vendor technical details.
Detection Methods for CVE-2026-49183
Indicators of Compromise
- Unexpected child processes spawned by the Clipboard User Service (cbdhsvc) or related clipboard host processes running under SYSTEM.
- New service creation, scheduled task registration, or token manipulation events shortly after clipboard-related activity from a standard user session.
- Repeated crashes or restarts of the Clipboard Server component, which may indicate failed race condition attempts.
Detection Strategies
- Hunt for standard user processes making high-frequency clipboard API calls immediately followed by privileged process creation.
- Correlate Windows Security event ID 4688 (process creation) with event ID 4672 (special privileges assigned) originating from user sessions that should not require elevation.
- Baseline normal Clipboard Server behavior and alert on anomalies such as unusual thread counts, handle duplication, or cross-session object access.
Monitoring Recommendations
- Ingest Sysmon process creation, image load, and handle events from all Windows endpoints into a centralized analytics platform.
- Monitor for privilege escalation patterns following interactive user logons, especially on multi-user systems such as Remote Desktop Session Hosts.
- Track Microsoft patch deployment status across the fleet to identify unpatched Windows 10, Windows 11, and Windows Server hosts.
How to Mitigate CVE-2026-49183
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2026-49183 Advisory to all affected Windows 10, Windows 11, and Windows Server hosts.
- Prioritize patching of multi-user systems such as Remote Desktop Session Hosts, Virtual Desktop Infrastructure, and terminal servers where local attackers are more prevalent.
- Audit local account inventories and remove unnecessary interactive logon rights to reduce the pool of potential attackers.
Patch Information
Microsoft has published the vendor advisory at Microsoft CVE-2026-49183 Advisory. Consult the advisory for the specific Knowledge Base article and cumulative update numbers that correspond to each affected build. Install the update through Windows Update, Windows Server Update Services, or your enterprise patch management platform.
Workarounds
- No official workaround has been published by Microsoft. Applying the security update is the recommended remediation.
- Where patching must be delayed, restrict interactive and remote interactive logon to trusted administrative accounts using Group Policy.
- Enforce application control policies such as Windows Defender Application Control to limit which binaries unprivileged users can execute on affected hosts.
# Verify installed updates on a Windows host
wmic qfe list brief /format:table
# PowerShell equivalent to check for the KB associated with the fix
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
