CVE-2010-3971

EXPLOITED

Internet Explorer 6-8 - Use-After-Free in CSS Parser via Self-Referential @import Rule

Title source: llm
STIX 2.1

Exploitation Summary

CVE-2010-3971 has been observed exploited in the wild (reported by VulnCheck KEV). EIP tracks 5 public exploits from researchers including Metasploit, Nephi Johnson, WooYun, including a Metasploit module exploits/windows/browser/ms11_003_ie_css_import.

AI-analyzed exploit summary This Metasploit module exploits a use-after-free vulnerability in Internet Explorer's CSS recursive import handling (CVE-2010-3971) to achieve remote code execution. It leverages heap spraying and ROP techniques with .NET 2.0's mscorie.dll to bypass DEP and ASLR.

Description

Use-after-free vulnerability in the CSharedStyleSheet::Notify function in the Cascading Style Sheets (CSS) parser in mshtml.dll, as used in Microsoft Internet Explorer 6 through 8 and other products, allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a self-referential @import rule in a stylesheet, aka "CSS Memory Corruption Vulnerability."

Exploits (5)

exploitdb WORKING POC VERIFIED
by Metasploit · rubyremotewindows
https://www.exploit-db.com/exploits/16533

This Metasploit module exploits a use-after-free vulnerability in Internet Explorer's CSS recursive import handling (CVE-2010-3971) to achieve remote code execution. It leverages heap spraying and ROP techniques with .NET 2.0's mscorie.dll to bypass DEP and ASLR.

Classification
Working Poc 100%
Attack Type
Rce
Complexity
Complex
Reliability
Reliable
Target: Microsoft Internet Explorer 6-8
No auth needed
Prerequisites: .NET Framework 2.0.50727 installed on target · Target must visit malicious webpage
devstral-2 · analyzed Feb 16, 2026 Full analysis →
exploitdb WORKING POC VERIFIED
by Nephi Johnson · rubyremotewindows
https://www.exploit-db.com/exploits/15746

This exploit targets a vulnerability in Internet Explorer (CVE-2010-3971) using a heap spray technique to achieve remote code execution. It serves malicious HTML and CSS content via a TCP server to trigger the vulnerability and execute arbitrary shellcode (calc.exe in this case).

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: Internet Explorer (versions affected by CVE-2010-3971)
No auth needed
Prerequisites: Victim must visit the malicious server · Internet Explorer with vulnerable version
devstral-2 · analyzed Feb 16, 2026 Full analysis →
exploitdb WORKING POC VERIFIED
by WooYun · htmldoswindows
https://www.exploit-db.com/exploits/15708

This exploit leverages a CSS import recursion vulnerability in Internet Explorer to cause a denial-of-service (DoS) condition. The recursive @import rules in the CSS file trigger a stack overflow, crashing the browser.

Classification
Working Poc 90%
Attack Type
Dos
Complexity
Trivial
Reliability
Reliable
Target: Microsoft Internet Explorer (versions prior to the fix)
No auth needed
Prerequisites: Victim must open the malicious HTML file in a vulnerable version of Internet Explorer
devstral-2 · analyzed Feb 16, 2026 Full analysis →
nomisec WORKING POC 2 stars
by nektra · poc
https://github.com/nektra/CVE-2010-3971-hotpatch

This repository contains a functional exploit PoC for CVE-2010-3971, targeting a vulnerability in Internet Explorer's mshtml.dll. The code hooks the CStyleSheet::Notify function to demonstrate exploitation, likely leading to remote code execution.

Classification
Working Poc 90%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: Internet Explorer (mshtml.dll)
No auth needed
Prerequisites: Internet Explorer running on the target system · Access to mshtml.dll and its symbols
devstral-2 · analyzed Feb 18, 2026 Full analysis →
metasploit WORKING POC GOOD
by passerby, d0c_s4vage, jduck · rubypocwin
https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/browser/ms11_003_ie_css_import.rb

This Metasploit module exploits a use-after-free vulnerability in Microsoft Internet Explorer (CVE-2010-3971) by leveraging recursive CSS imports to corrupt memory, achieving arbitrary code execution via heap spraying and ROP chains targeting mscorie.dll to bypass DEP/ASLR.

Classification
Working Poc 100%
Attack Type
Rce
Complexity
Complex
Reliability
Reliable
Target: Microsoft Internet Explorer 6, 7, 8
No auth needed
Prerequisites: .NET Framework 2.0.50727 installed · Target must visit a malicious webpage
devstral-2 · analyzed Feb 19, 2026 Full analysis →

References (16)

Core 16
Core References
US Government Resource third-party-advisory x_refsource_cert-vn
http://www.kb.cert.org/vuls/id/634956
Exploit exploit x_refsource_exploit-db
http://www.exploit-db.com/exploits/15746
Vendor Advisory x_refsource_confirm
http://support.avaya.com/css/P8/documents/100127294
Third Party Advisory vdb-entry x_refsource_vupen
http://www.vupen.com/english/advisories/2011/0318
Exploit exploit x_refsource_exploit-db
http://www.exploit-db.com/exploits/15708
Vendor Advisory vdb-entry x_refsource_vupen
http://www.vupen.com/english/advisories/2010/3156
Third Party Advisory, VDB Entry vdb-entry x_refsource_sectrack
http://www.securitytracker.com/id?1024922
Exploit mailing-list x_refsource_fulldisc
http://seclists.org/fulldisclosure/2010/Dec/110
Third Party Advisory, VDB Entry vdb-entry x_refsource_bid
http://www.securityfocus.com/bid/45246
Third Party Advisory, VDB Entry vdb-entry signature x_refsource_oval
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12382
Vendor Advisory third-party-advisory x_refsource_secunia
http://secunia.com/advisories/42510

Scores

EPSS 0.8560
EPSS Percentile 99.4%

Details

VulnCheck KEV 2011-03-08
CWE
CWE-399
Status published
Products (2)
microsoft/internet_explorer 7
microsoft/internet_explorer 8
Published Dec 22, 2010
Tracked Since Feb 18, 2026