CVE-2026-62902 Overview
CVE-2026-62902 is an information disclosure vulnerability in Microsoft .NET caused by inclusion of functionality from an untrusted control sphere [CWE-693]. An unauthorized attacker can disclose sensitive information over a network when a user is tricked into interacting with attacker-controlled content. The flaw requires user interaction, meaning exploitation depends on convincing a target to open or execute a crafted resource loaded by a vulnerable .NET application.
Critical Impact
Successful exploitation exposes confidential data processed by .NET applications to remote, unauthenticated attackers over a network.
Affected Products
- Microsoft .NET (see the Microsoft Security Update Guide for affected versions)
Discovery Timeline
- 2026-08-11 - CVE-2026-62902 published to NVD
- 2026-08-13 - Last updated in NVD database
Technical Details for CVE-2026-62902
Vulnerability Analysis
The vulnerability is classified under [CWE-693] Protection Mechanism Failure, specifically involving inclusion of functionality from an untrusted control sphere. A vulnerable .NET component loads or executes code, resources, or configuration originating from a source outside the trust boundary. When this untrusted content is processed, the application inadvertently exposes information that should remain confidential.
The attack is network-based and requires user interaction. An attacker cannot trigger the flaw without a user opening a document, visiting a page, or launching an application that references the untrusted resource. The scope is unchanged, and the impact is limited to confidentiality; integrity and availability are not affected.
Because the vulnerability lives inside the .NET runtime or an associated library, any managed application that processes external content through the affected code path inherits the risk. This includes desktop, server, and developer-tooling scenarios that consume remote or user-supplied inputs.
Root Cause
The root cause is a protection mechanism failure in how .NET distinguishes between trusted and untrusted content. Functionality sourced from an untrusted sphere is included and executed without adequate boundary enforcement, resulting in information leakage. Microsoft has not published detailed root-cause internals beyond the advisory.
Attack Vector
Exploitation follows a network delivery path with user interaction. An attacker hosts crafted content that references or embeds functionality processed by a vulnerable .NET application. When a targeted user opens the content, the runtime pulls in the untrusted functionality and leaks information observable to the attacker. No credentials are required. The vulnerability manifests through the .NET content-handling pipeline. See the Microsoft Security Update Guide for vendor-provided technical detail.
Detection Methods for CVE-2026-62902
Indicators of Compromise
- Outbound network requests from dotnet.exe, w3wp.exe, or other .NET host processes to unexpected external endpoints following user interaction with untrusted files
- Unusual loading of remote assemblies, XML, or configuration content by managed applications
- Anomalous DNS lookups originating from processes hosting .NET workloads shortly after opening received documents or links
Detection Strategies
- Inventory endpoints and servers running .NET runtimes and correlate against the patched builds listed by Microsoft
- Hunt for .NET applications loading remote URIs through System.Xml, System.Net, or reflection-based assembly loading APIs
- Alert on processes hosting the CLR making egress connections to low-reputation domains after user-initiated file opens
Monitoring Recommendations
- Capture process, network, and file telemetry from .NET host processes and forward to a centralized analytics platform for retrospective hunting
- Monitor web proxies and DNS logs for requests generated by managed applications immediately after email or web interaction
- Track patch deployment status across the fleet to identify systems still exposed to CVE-2026-62902
How to Mitigate CVE-2026-62902
Immediate Actions Required
- Apply the security updates published in the Microsoft Security Update Guide for all affected .NET versions
- Prioritize patching on systems that process untrusted external content, including developer workstations and internet-facing application servers
- Notify users to avoid opening unexpected files or links delivered through email or messaging that target .NET-based tooling
Patch Information
Microsoft has released security updates addressing CVE-2026-62902. Refer to the Microsoft Security Update Guide for the specific .NET SDK and runtime versions that contain the fix. Apply updates through Windows Update, dotnet installers, or your enterprise patch management workflow.
Workarounds
- Restrict outbound network access from workstations and servers running .NET applications to reduce data-exfiltration channels
- Enforce email and web filtering to block delivery of crafted documents that trigger the vulnerable code path
- Apply application allowlisting to prevent execution of unsigned or untrusted .NET binaries until patching completes
# Verify installed .NET runtime versions across the fleet
dotnet --list-runtimes
dotnet --list-sdks
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
