CVE-2014-1776
Microsoft Internet Explorer Memory Corruption Vulnerability
Description
CVE-2014-1776 is a CRITICAL use-after-free memory corruption vulnerability (CWE-416) in Microsoft Internet Explorer versions 6 through 11. The vulnerability allows remote attackers to execute arbitrary code in the context of the current user by exploiting a use-after-free condition triggered when processing specially crafted web content. With a CVSS 3.1 score of 9.8, this zero-day vulnerability was actively exploited in targeted attacks before a patch was available, prompting an emergency out-of-band security update from Microsoft (MS14-021). CISA added CVE-2014-1776 to its Known Exploited Vulnerabilities catalog on January 28, 2022, with a remediation deadline of July 28, 2022. The EPSS score of 0.81844 (99.18th percentile) reflects the historical severity and continued relevance of this exploit.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| microsoft | internet explorer | 6; 7; 8; 9; 10; 11 |
References
- http://blogs.technet.com/b/srd/archive/2014/04/30/protection-strategies-for-the-security-advisory-2963983-ie-0day.aspx(Broken Link, Mitigation)
- http://secunia.com/advisories/57908(Broken Link)
- http://securitytracker.com/id?1030154(Broken Link, Third Party Advisory, VDB Entry)
- http://www.fireeye.com/blog/uncategorized/2014/04/new-zero-day-exploit-targeting-internet-explorer-versions-9-through-11-identified-in-targeted-attacks.html(Broken Link)
- http://www.kb.cert.org/vuls/id/222929(Mitigation, Third Party Advisory, US Government Resource)
- http://www.osvdb.org/106311(Broken Link)
- http://www.securityfocus.com/bid/67075(Broken Link, Third Party Advisory, VDB Entry)
- http://www.signalsec.com/cve-2014-1776-ie-0day-analysis/(Exploit, Third Party Advisory)
- https://docs.microsoft.com/en-us/security-updates/securitybulletins/2014/ms14-021(Patch, Vendor Advisory)
- https://technet.microsoft.com/library/security/2963983(Mitigation, Patch, Vendor Advisory)
- https://www.vicarius.io/vsociety/posts/cve-2014-1776-use-after-free-vulnerability-in-microsoft-internet-explorer-detection-script(Third Party Advisory)
- https://www.vicarius.io/vsociety/posts/cve-2014-1776-use-after-free-vulnerability-in-microsoft-internet-explorer-mitigation-scripts(Third Party Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2014-1776(US Government Resource)
Weakness Type
CWE-416: Use After Free
Use After Free (UAF) is a critical memory safety vulnerability that occurs when software continues to reference a pointer after the memory it points to has been freed (deallocated). Once memory is freed, it may be reallocated for different purposes by the memory allocator. If the original (now dangling) pointer is subsequently dereferenced, the program may read from or write to memory that now contains entirely different data structures, leading to data corruption, information disclosure, or arbitrary code execution. UAF vulnerabilities are especially prevalent in complex applications with manual memory management, such as web browsers, document renderers, and operating system kernels, where intricate object lifecycle management creates opportunities for dangling pointer conditions.
In CVE-2014-1776, the use-after-free condition exists in Internet Explorer's handling of CMarkup objects within the MSHTML rendering engine. When processing specially crafted HTML content, IE frees a CMarkup object but retains a reference to it. Subsequent operations dereference this stale pointer, allowing an attacker to control the contents of the freed memory through heap manipulation techniques such as heap spraying. By carefully arranging attacker-controlled data (including crafted virtual function table pointers) in the freed memory region, the attacker achieves code execution when the dangling pointer is used to call a virtual method. Learn more about Use After Free (CWE-416)
Impact Analysis
CVE-2014-1776 has a CVSS 3.1 base score of 9.8 (CRITICAL), reflecting the devastating impact of browser-based remote code execution.
Confidentiality (High): Successful exploitation allows the attacker to execute arbitrary code with the privileges of the Internet Explorer process, which typically runs under the logged-in user's context. This grants access to all files, credentials, browser stored passwords, cookies, session tokens, and data accessible to that user. In enterprise environments where users browse with domain credentials, the attacker can harvest authentication tokens for lateral movement across the corporate network.
Integrity (High): Code execution in the browser context allows the attacker to install malware, modify local files, alter browser settings, inject content into other web sessions, and establish persistence mechanisms. The attacker can deploy Remote Access Trojans (RATs), keyloggers, or credential-harvesting implants. If the user has administrative privileges, the attacker gains full system control and can modify any system configuration.
Availability (High): The attacker can crash the browser, corrupt user data, deploy ransomware, or use the compromised system as a launching point for denial-of-service attacks. In targeted attack scenarios, the exploitation was observed as part of campaigns aimed at disrupting specific organizations' operations and exfiltrating sensitive data.
Scope (Unchanged): While the CVSS scope is unchanged, practical exploitation frequently extends beyond the browser sandbox (particularly in older IE versions with weaker sandboxing). Combined with privilege escalation, the impact reaches the full operating system. The EPSS score of 0.81844 (99.18th percentile) confirms the extreme exploitation probability for this vulnerability.
Exploit Maturity
Active Zero-Day Exploitation: CVE-2014-1776 was exploited as a zero-day vulnerability in targeted attacks before Microsoft released patches. FireEye initially disclosed the attacks, identifying sophisticated exploitation targeting Internet Explorer versions 9 through 11 in campaigns attributed to advanced persistent threat (APT) groups. The zero-day status prompted CERT/CC to issue an advisory and Microsoft to release an emergency out-of-band patch.
Ransomware Association: The CISA KEV catalog does not directly associate CVE-2014-1776 with ransomware campaigns. However, browser-based remote code execution vulnerabilities are foundational tools in many attack chains that ultimately lead to ransomware deployment.
Public Exploits: Public exploit analysis and proof-of-concept code are available, including a detailed technical analysis on SignalSec. The Microsoft Security Bulletin MS14-021 provides official patch information, and CERT/CC published vulnerability note VU#222929 with mitigation guidance.
EPSS Context: The EPSS score of 0.81844 (99.18th percentile) places this vulnerability in the top 1% of all CVEs for exploitation likelihood, reflecting both the historical exploitation and the continued presence of unpatched legacy IE installations.
KEV Deadline: The CISA remediation deadline was July 28, 2022. Organizations still running legacy Internet Explorer should migrate to supported browsers immediately.
Remediation
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Apply Microsoft security update MS14-021 immediately. Install the cumulative security update for Internet Explorer provided through the Microsoft Security Bulletin MS14-021 or subsequent cumulative updates. This patch corrects the use-after-free condition in the MSHTML rendering engine's handling of CMarkup objects.
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Migrate away from Internet Explorer entirely. Internet Explorer has reached end of life and no longer receives security updates. Transition all users to a modern, supported browser such as Microsoft Edge, Chrome, or Firefox to eliminate exposure to this and hundreds of other unpatched IE vulnerabilities.
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Enable Enhanced Protected Mode (EPM) in Internet Explorer. If IE must be used temporarily, enable Enhanced Protected Mode in Internet Options > Advanced tab. EPM runs IE tabs in a more restricted AppContainer sandbox that limits the impact of successful exploitation by restricting access to the filesystem and registry.
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Deploy the Enhanced Mitigation Experience Toolkit (EMET). For legacy systems that cannot be immediately upgraded, EMET provides additional exploit mitigations including heap spray protection, DEP enforcement, and ROP mitigations that make exploitation of memory corruption vulnerabilities significantly more difficult.
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Implement network-level web filtering. Deploy web proxies or secure web gateways that can inspect and filter malicious web content before it reaches the browser. URL reputation filtering can block access to known exploit delivery domains and reduce the overall attack surface.
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Restrict user browsing privileges. Ensure users do not browse the web with administrative credentials. Running IE as a standard user limits the impact of exploitation to the user's context rather than providing immediate system-level access to the attacker.
Technical Details
CVE-2014-1776 is a use-after-free vulnerability in the MSHTML rendering engine (mshtml.dll) used by Microsoft Internet Explorer versions 6 through 11. The vulnerability exists in the handling of CMarkup objects during the processing of specially crafted HTML content. When the browser renders attacker-controlled content, a CMarkup object is freed prematurely while references to it still exist elsewhere in the rendering pipeline.
The exploitation technique leverages heap spraying to populate the freed memory region with attacker-controlled data. Using JavaScript or ActionScript (via Flash), the attacker allocates many objects of the same size as the freed CMarkup object, eventually occupying the freed memory with data containing a crafted virtual function table (vtable) pointer. When IE subsequently dereferences the dangling pointer and calls a virtual method through the corrupted vtable, execution redirects to attacker-controlled code.
The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) indicates that exploitation requires only that the victim visit a malicious web page — no authentication or additional user interaction is needed beyond navigating to the attacker's content. The attack complexity is low because reliable exploitation techniques for IE UAF vulnerabilities were well-established by 2014, with heap spray techniques providing consistent exploitation across different Windows versions.
The original zero-day exploitation was observed using a combination of the IE UAF vulnerability with an Adobe Flash component to achieve reliable heap spray and code execution. Microsoft's analysis confirmed the vulnerability affected all supported IE versions at the time, leading to the rare issuance of an emergency out-of-band security update that included support for Windows XP despite it having officially reached end of life.
Frequently Asked Questions
What is CVE-2014-1776?
CVE-2014-1776 is a critical use-after-free memory corruption vulnerability in Microsoft Internet Explorer versions 6 through 11. It allows remote attackers to execute arbitrary code by luring victims to malicious web pages that trigger a use-after-free condition in the MSHTML rendering engine. The vulnerability was exploited as a zero-day in targeted attacks and prompted an emergency out-of-band patch from Microsoft.
Which Internet Explorer versions are affected by CVE-2014-1776?
All versions of Internet Explorer from 6 through 11 are affected by CVE-2014-1776. This spans every version of IE that was in use at the time of disclosure. The active zero-day exploitation primarily targeted IE 9 through 11, but the underlying vulnerability existed in all versions. Microsoft released patches for all supported IE versions, including an exceptional patch for IE on the already end-of-life Windows XP.
How do I fix CVE-2014-1776?
Apply Microsoft security update MS14-021 or any subsequent cumulative IE update that includes this fix. More importantly, migrate away from Internet Explorer entirely, as it has reached end of life and no longer receives security updates. If IE must be used temporarily, enable Enhanced Protected Mode and deploy EMET to reduce exploitation risk. Organizations should prioritize migrating all users to modern supported browsers.
How severe is CVE-2014-1776?
CVE-2014-1776 is rated CRITICAL with a CVSS 3.1 score of 9.8. Its EPSS score of 0.81844 (99.18th percentile) reflects extreme exploitation probability. The vulnerability was exploited as a zero-day by APT groups in targeted attacks, was significant enough to prompt an emergency Microsoft patch, and CISA has included it in the Known Exploited Vulnerabilities catalog. Any system still running Internet Explorer without this patch is at severe risk.
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