CVE-2011-1271: Microsoft .NET Framework

High severity, CVSS 7.7. EPSS: 20.1% chance of exploitation in the next 30 days.

The JIT compiler in Microsoft .NET Framework 3.5 Gold and SP1, 3.5.1, and 4.0, when IsJITOptimizerDisabled is false, does not properly handle expressions related to null strings, which allows context-dependent attackers to bypass intended access restrictions, and consequently execute arbitrary code, in opportunistic circumstances by leveraging a crafted application, as demonstrated by (1) a crafted XAML browser application (aka XBAP), (2) a crafted ASP.NET application, or (3) a crafted .NET Framework application, aka ".NET Framework JIT Optimization Vulnerability."

Affected products

• Microsoft .NET Framework: version 4.0 only; version 3.5.1 only; version 2.0 only; version 3.5 only

Published 2011-05-10. Last modified 2026-06-16.