CVE-2013-2551

CVE-2013-2551: Microsoft Internet Explorer Use-After-Free Vulnerability

AI-generated analysis based on the vulnerability data on this page.

Summary

A use-after-free vulnerability in Microsoft Internet Explorer 6 through 10 enables remote code execution when a user visits a crafted web site. The vulnerability was demonstrated by VUPEN during the Pwn2Own competition at CanSecWest 2013 and is tracked as CVE-2013-2551, distinct from CVE-2013-1308 and CVE-2013-1309.

Background

Use-after-free vulnerabilities occur when a program continues to use a pointer after the memory it references has been freed. In web browsers, these flaws are particularly dangerous because attackers can manipulate the JavaScript heap to reclaim the freed memory with controlled data, leading to type confusion and arbitrary code execution. Internet Explorer's legacy memory management architecture in versions 6 through 10 made it susceptible to this class of vulnerability.

Root Cause

The vulnerability is classified as CWE-416: Use After Free. The root cause lies in Internet Explorer's improper handling of object lifecycle management during DOM (Document Object Model) operations. Specifically, the browser fails to validate that an object still exists before accessing it, allowing a dangling pointer to be dereferenced. This can occur when JavaScript manipulates DOM elements in ways that trigger premature object destruction, leaving a reference that the renderer later attempts to access.

Impact

This vulnerability carries a CVSS v2 score of 9.3 (AV:N/AC:M/Au:N/C:C/I:C/A:C) and a CVSS v3 score of 8.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H). The metrics indicate:

• Network-based attack vector: Exploitation requires the victim to visit a malicious web page.
• Medium attack complexity (v2) / Low (v3): The vulnerability can be reliably exploited.
• No authentication required: The attacker does not need valid credentials.
• Complete confidentiality, integrity, and availability impact: Successful exploitation grants the attacker full control over the affected system.

The high EPSS score of 0.74096 (99.4th percentile) and inclusion in CISA's Known Exploited Vulnerabilities (KEV) catalog confirm active, real-world exploitation.

Exploitation Walkthrough

From a defensive perspective, exploitation typically follows this pattern:

1. The attacker crafts a malicious web page containing JavaScript designed to trigger specific DOM operations.
2. The user visits the page via an affected version of Internet Explorer.
3. The JavaScript code manipulates DOM objects in a sequence that causes a heap allocation to be freed prematurely.
4. Before the browser updates its references, the freed memory is reclaimed and populated with attacker-controlled data.
5. When the browser later dereferences the original pointer, it executes code from the attacker-controlled memory region.

Ethics caveat: This walkthrough is provided for defensive awareness only. The specific vulnerability was disclosed responsibly through Pwn2Own and subsequently patched by Microsoft. Attempting to exploit unpatched systems without authorization is illegal and unethical.

Affected and Patched Versions

Affected products:

• Microsoft Internet Explorer 6
• Microsoft Internet Explorer 7
• Microsoft Internet Explorer 8
• Microsoft Internet Explorer 9
• Microsoft Internet Explorer 10

Affected operating systems:

• Windows XP SP2 and SP3
• Windows Server 2003 SP2
• Windows Vista SP2
• Windows Server 2008 SP2
• Windows 7 SP1
• Windows Server 2008 R2 SP1
• Windows 8
• Windows RT
• Windows Server 2012

Patched versions: Microsoft addressed this vulnerability in Security Bulletin MS13-037 (May 2013).

Remediation

1. Upgrade or replace Internet Explorer: Apply the patches from Microsoft Security Bulletin MS13-037. Organizations still running legacy Internet Explorer versions should migrate to modern browsers such as Microsoft Edge.
2. Compensating controls:
   • Deploy Microsoft Enhanced Mitigation Experience Toolkit (EMET) to harden legacy systems.
   • Enable Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) where supported.
   • Restrict or disable Active Scripting in Internet Explorer security zones for untrusted sites.
   • Implement application whitelisting to prevent unauthorized browser execution.

Detection

• Monitor web proxy logs for suspicious referrer patterns or visits to known exploit-kit landing pages.
• Enable endpoint detection and response (EDR) heuristics focused on memory allocation anomalies in browser processes.
• Leverage network intrusion detection systems (IDS) with signatures for exploit-kit traffic associated with CVE-2013-2551.
• Review CISA's KEV catalog for threat intelligence on active exploitation campaigns.

Assessment

With an EPSS score of 0.74096 and a 99.4th percentile ranking, this vulnerability is among the most likely to be exploited in the wild. Its inclusion in CISA's KEV catalog since 2022-03-28 confirms ongoing relevance for threat actors. Two key lessons emerge:

1. Browser security is endpoint security: A single browser vulnerability can provide complete system compromise, making patch management for web browsers a critical priority.
2. Legacy software carries persistent risk: Even vulnerabilities disclosed in 2013 remain relevant when organizations continue to run unsupported software configurations.

References

• http://h30499.www3.hp.com/t5/HP-Security-Research-Blog/Pwn2Own-2013/ba-p/5981157
• http://twitter.com/VUPEN/statuses/309479075385327617
• http://twitter.com/thezdi/statuses/309452625173176320
• http://www.us-cert.gov/ncas/alerts/TA13-134A
• https://docs.microsoft.com/en-us/security-updates/securitybulletins/2013/ms13-037
• https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A16317
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2013-2551