CVE-2017-0210

What Is Internet Explorer?

Internet Explorer (IE) enforces a security model based on zones — Internet, Intranet, Trusted Sites, and Local Machine — and the Same-Origin Policy (SOP) that prevents pages from one domain from accessing content or executing code in the context of another. These security boundaries are critical for containing browser-based exploits: an attacker page in the Internet zone should not be able to access or manipulate pages in the Intranet or Local Machine zone. Flaws in IE's zone/origin enforcement have historically been used to escalate from restricted execution contexts to less restricted ones, amplifying the impact of other vulnerabilities.

Overview

CVE-2017-0210 is a privilege escalation vulnerability in Internet Explorer caused by improper enforcement of cross-domain policies. An attacker who hosts a malicious web page can exploit this flaw to access information from another security zone — enabling zone boundary escalation from the Internet zone toward the Local Machine or Intranet zone. Patched in the April 2017 security update for Internet Explorer. The CVSS score of 8.8 (full C/I/A impact) reflects that the policy bypass can be chained with an IE RCE vulnerability to escape sandbox restrictions and achieve broader system access. CISA added CVE-2017-0210 to the KEV catalog in May 2022.

Affected Versions

Affected on Windows 7 SP1, Windows 8.1, Windows RT 8.1, Windows Server 2008 R2 SP1, Windows Server 2012, Windows Server 2012 R2, Windows 10 (all versions prior to patch), and Windows Server 2016.

Technical Details

Root Cause: Cross-Domain Policy Bypass

CVE-2017-0210 is an origin validation error (CWE-346) in Internet Explorer's enforcement of cross-domain security policies. IE implements the Same-Origin Policy and zone-based security to prevent pages from one origin accessing resources in another. The vulnerability exists in how IE validates the origin of scripting operations or object references across domain boundaries — under specific conditions, the check is performed incorrectly or skipped, allowing an attacker-controlled page to access or interact with content that should be restricted by zone policy.

Exploitation pattern:

• The attacker hosts a malicious page in the Internet zone
• The page exploits the cross-domain policy bypass to access content, read information, or execute actions in a higher-privilege zone (Intranet or Local Machine)
• In a chained attack, the zone escalation is combined with an IE memory corruption RCE vulnerability — the RCE executes code inside the sandbox, and the policy bypass provides a path to escape zone restrictions

High CVSS despite "privilege escalation" classification: The CVSS score of 8.8 with full C:H/I:H/A:H reflects that a successful cross-domain policy bypass in IE can result in code execution in a higher-privilege zone. In IE's architecture, the Local Machine zone has substantially fewer restrictions than the Internet zone, so escalating from Internet to Local Machine effectively grants code execution capabilities beyond what the initial RCE vulnerability provides.

Attack Characteristics

Discovery

Reported to Microsoft through coordinated disclosure and patched in the April 2017 Patch Tuesday security update.

Exploitation Context

• Chained exploitation: CVE-2017-0210 is primarily valuable as part of an exploit chain — an attacker uses an IE memory corruption vulnerability (such as CVE-2017-0149 or CVE-2017-0222) to get code execution inside the sandbox, then uses CVE-2017-0210 to bypass the cross-domain policy and elevate privileges out of the sandboxed zone; this two-step pattern was common in IE exploit kit deployments
• Exploit kit incorporation: Exploit kits targeting IE frequently combined multiple vulnerabilities: an RCE for code execution and a privilege escalation for sandbox escape; CVE-2017-0210 fit this role in the 2017 exploit kit ecosystem
• Enterprise IE targeting: Corporate environments running IE 11 in Enterprise Mode for legacy intranet applications were at risk — the cross-domain bypass could expose intranet resources to attacker-controlled content from the internet
• CISA KEV (2022): Added May 2022 reflecting confirmed active exploitation years after the patch, consistent with the long tail of IE exploitation against organizations that did not prioritize IE patching

Remediation

1. Apply April 2017 security update — install the April 2017 Cumulative Security Update for Internet Explorer on all Windows systems.

2. Migrate from Internet Explorer — IE reached end of life on June 15, 2022; migrate all users and applications to Microsoft Edge (with IE mode if needed for legacy compatibility).

3. Configure Enhanced Protected Mode — enable Enhanced Protected Mode in IE 11 to limit the damage from zone escalation attacks by restricting what elevated-zone code can access.

4. Restrict IE zone configuration — use Group Policy to enforce stricter security settings for the Internet zone in IE, limiting what scripts can do even within a single zone.

5. Enable Windows Defender SmartScreen — SmartScreen in IE blocks known malicious URLs that serve exploit kit payloads, providing network-level defense against drive-by exploitation.