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Vulnerability record · CVE-2011-1271 · published 10 May 2011

CVE-2011-1271: Microsoft .net framework permissions and access controls vulnerability

Microsoft · .Net Framework

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."

7.7 CVSS 3.1 High EPSS 20% · top 2.6% CWE-264 · Permissions and access controlsCWE-476 · NULL pointer dereference
7.7CVSS 3.1 base score, v2 5.1
20%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References, 2 tagged exploit
16 Jun 2026Last modified by NVD

Description

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."

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://stackoverflow.com/questions/2135509/bug-only-occurring-when-compile-optimization-enabled/ Exploit
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2011/ms11-044
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12686
http://stackoverflow.com/questions/2135509/bug-only-occurring-when-compile-optimization-enabled/ Exploit
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2011/ms11-044
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12686

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2011-1271), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.