CVE-2026-50307 Overview
CVE-2026-50307 is a use-after-free vulnerability [CWE-416] in the Microsoft Windows TCP/IP stack. An authorized local attacker can exploit the flaw to elevate privileges on affected Windows client and server systems. Successful exploitation grants the attacker high impact to confidentiality, integrity, and availability of the target host. The issue affects supported versions of Windows 10, Windows 11, and Windows Server. Microsoft published the advisory through the Microsoft Security Response Center (MSRC) and released fixes as part of a security update.
Critical Impact
A local, low-privileged user can trigger a use-after-free condition in the Windows TCP/IP component to gain elevated privileges on the host, enabling full system compromise.
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, Server 2022, and Server 2025
Discovery Timeline
- 2026-07-14 - CVE-2026-50307 published to NVD
- 2026-07-16 - Last updated in NVD database
Technical Details for CVE-2026-50307
Vulnerability Analysis
The vulnerability resides in the Windows TCP/IP networking stack, a kernel-mode component (tcpip.sys) responsible for processing IPv4 and IPv6 traffic. A use-after-free condition [CWE-416] occurs when the component references memory after it has been released. An authorized local attacker can trigger this condition to corrupt kernel memory. Successful exploitation results in local privilege escalation to SYSTEM context, giving the attacker full control of the host.
Because the flaw is exposed locally rather than remotely, the attacker must already hold valid credentials on the target. The vulnerability is well-suited for post-compromise activity, such as escalating from a standard user or service account obtained through phishing, credential theft, or an initial foothold.
Root Cause
The root cause is a lifetime management error in a TCP/IP kernel object. When the object is freed, one or more references remain valid and are later dereferenced. Reallocating the freed slab with attacker-controlled data allows the adversary to influence subsequent operations that treat the memory as a valid structure, leading to arbitrary kernel read/write and privilege escalation.
Attack Vector
Exploitation requires local access with low privileges and no user interaction. The attacker issues crafted socket operations or networking API calls from user mode that reach the vulnerable code path in tcpip.sys. By racing the free and reallocating the object with controlled content, the attacker manipulates kernel structures to gain code execution in kernel context. No public proof-of-concept or in-the-wild exploitation has been reported at the time of publication, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The current EPSS probability is 0.2%.
No verified proof-of-concept code is available. Refer to the Microsoft Security Update CVE-2026-50307 advisory for authoritative technical details.
Detection Methods for CVE-2026-50307
Indicators of Compromise
- Unexpected SYSTEM-level processes spawned by non-administrative user sessions shortly after socket-heavy activity.
- Kernel bug checks or tcpip.sys crash dumps on hosts that were otherwise stable.
- New services, scheduled tasks, or driver installations following anomalous local logons.
Detection Strategies
- Hunt for token manipulation and process parent-child anomalies where a low-privileged user's process suddenly executes with elevated integrity.
- Correlate Windows Event ID 4672 (special privileges assigned) with unexpected user contexts.
- Baseline networking API usage per user and flag outliers issuing high volumes of raw socket or IOCTL calls.
Monitoring Recommendations
- Ingest Windows Security, System, and Sysmon logs into a centralized analytics platform for correlation across hosts.
- Alert on repeated tcpip.sys crashes, WHEA errors, or unexpected reboots that may indicate exploitation attempts.
- Track patch compliance for the July 2026 Microsoft security updates across all Windows 10, 11, and Server assets.
How to Mitigate CVE-2026-50307
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-50307 to all affected Windows 10, Windows 11, and Windows Server systems.
- Prioritize patching multi-user hosts, jump servers, and RDS/Citrix environments where multiple low-privileged users share a machine.
- Audit local accounts and remove unnecessary interactive logon rights to reduce the pool of potential attackers.
Patch Information
Microsoft has issued security updates for all supported affected platforms through the standard Windows Update channels and the Microsoft Update Catalog. Refer to the Microsoft Security Update CVE-2026-50307 advisory for KB article numbers and package downloads corresponding to each Windows build.
Workarounds
- No official workaround is documented by Microsoft; patching is the only fully effective mitigation.
- Restrict local and interactive access to trusted administrators until updates are deployed.
- Enforce application allowlisting and endpoint protection policies to block execution of unknown local privilege escalation tooling.
# Verify patch deployment status on a Windows host
wmic qfe list brief /format:table
# Or using PowerShell to check installed hotfixes
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.
