CVE-2014-0257

This is a flaw in Microsoft .NET Framework, a Windows software component that many business applications rely on. It can let an attacker run their own software where the framework should have rejected it—like a building receptionist mistakenly allowing someone into restricted areas.

This matters if you use or run Microsoft .NET Framework on Windows computers or servers, including through older business applications that installed it as a dependency. Check both employee computers and servers hosting internal applications. It is only a risk through a crafted website or an application that exposes a COM server endpoint.

Public exploit code is available, so attackers have a starting point for abusing this flaw. Treat this as urgent because the affected versions are old and the vulnerability can lead to full control of an affected system.

Confirm exposure by inventorying installed .NET Framework releases across endpoints and servers, then compare them with the affected releases: 1.0 SP3, 1.1 SP1, 2.0 SP2, 3.5, 3.5.1, 4.0, 4.5, and 4.5.1. Apply the vendor remediation referenced by Microsoft Security Bulletin MS14-009; the provided patch finding does not specify fixed-version targets per branch, so use the update applicable to each supported Windows/.NET installation rather than assuming an in-place framework upgrade is sufficient.

If patching is delayed, reduce exposure to untrusted web content on affected machines and isolate applications that expose COM server endpoints from untrusted networks. After remediation, review endpoint and server telemetry for unexpected process launches, new accounts, unusual outbound connections, and changes to application services. CISA KEV does not list this CVE, so no CISA remediation due date is provided.

CVSS is 9.3 (Critical), with network attack vector, medium complexity, no authentication requirement, and complete confidentiality, integrity, and availability impact. The weakness is CWE-20 improper input validation, described as a type-traversal issue that fails to correctly determine whether a method is safe to execute. Public exploit code is available (two known exploits). EPSS predicts a 69.7% likelihood and places it in the 99th percentile, with a falling trend; this is predictive data, not confirmation of active exploitation. The CVE is not listed in CISA KEV, and the supplied findings do not confirm exploitation in the wild.