CVE-2015-0071: Microsoft Internet Explorer ASLR Bypass Vulnerability

CVE-2015-0071 is an address space layout randomization (ASLR) bypass vulnerability in Microsoft Internet Explorer. A remote attacker can trigger it by luring a user to a crafted web site, weakening a core memory-protection defense that makes reliable exploitation of other flaws harder. For IT and security teams, this matters because ASLR bypasses are often chained with separate memory-corruption bugs to achieve code execution in the browser process, increasing the chance of initial access on endpoints that still run the affected software.

Public detail is limited to the CISA description and the CWE classification; exact affected builds, attack primitives, and scoring must be confirmed against the vendor advisory. Treat any unpatched Internet Explorer instance as in-scope until you verify otherwise.

How it works

The weakness is classified as CWE-264 (Permissions, Privileges, and Access Controls). ASLR randomizes the base addresses of key modules and heaps so that an attacker cannot reliably predict where code or data will reside in memory. When that randomization can be bypassed, subsequent exploits become far more deterministic.

According to the CISA summary, Microsoft Internet Explorer allows remote attackers to bypass ASLR via a crafted web site. In practical terms, the attacker hosts or injects content that the browser renders; the content interacts with the vulnerable component in a way that leaks or forces predictable layout of memory regions. No further exploit mechanics are provided in the given facts, so defenders should not assume specific techniques such as heap spraying, info-leak primitives, or particular DOM objects—those details belong only in the vendor advisory or subsequent research. The result is simply that ASLR no longer provides the intended entropy, lowering the bar for a follow-on exploit.

Am I affected? How to find it in your systems

Internet Explorer historically shipped with Windows client and server editions and was often the default or fallback browser for internal web applications, ActiveX controls, and legacy line-of-business sites. Even after newer browsers became standard, IE components (including the Trident engine) could remain present and invocable by other processes or by user action.

• Inventory: Query software asset management, SCCM/ConfigMgr, Intune, or vulnerability scanners for any installation of Internet Explorer. Check both interactive desktop images and server SKUs that may host browser-based admin tools.
• Version and configuration: Compare installed IE builds against the fixed versions listed in the Microsoft advisory for CVE-2015-0071. Confirm whether Enhanced Protected Mode, 64-bit tab processes, or other mitigations were enabled; these settings can alter exploitability but do not replace the patch.
• Telemetry and logs: Look for unexpected crashes or hangs in iexplore.exe, especially following navigation to untrusted or newly registered domains. Endpoint detection platforms may surface memory-corruption or ASLR-related alerts; correlate those with web-proxy or DNS logs showing visits to suspicious sites. Absence of such signals does not prove safety—quiet reconnaissance is possible.

If your environment has fully migrated away from IE and the component is removed or blocked, residual risk is lower, but still verify that no legacy dependencies re-enable it.

How to remediate

Patch first. Apply the updates Microsoft released for this vulnerability exactly as described in the vendor advisory; CISA’s required action is simply “Apply updates per vendor instructions.” Use your standard test-and-deploy pipeline, prioritizing systems that still allow users to launch Internet Explorer or that render untrusted web content inside IE-based controls.

After patching, harden the browser attack surface for this class of issue:

• Enforce use of a modern, supported browser as the enterprise default and remove or disable Internet Explorer where business needs allow.
• Enable available platform mitigations (for example, Control Flow Guard, DEP, and high-entropy ASLR) on endpoints so that any residual memory-safety bugs are harder to exploit.
• Restrict or audit ActiveX, browser helper objects, and legacy add-ons that increase the amount of native code loaded into the browser process.
• Keep the OS and all browser-related redistributables current so that ASLR and other mitigations remain effective.

If you can't patch immediately

Compensating controls reduce—but do not eliminate—risk until the vendor update can be installed:

• Network segmentation and application control: Limit which users and machines can reach the public Internet with Internet Explorer; prefer allow-listing of approved browsers.
• Virtual patching / web filtering: Deploy proxy or DNS rules that block known-malicious or uncategorized sites; some web application firewalls or secure-web gateways can detect exploit kit patterns associated with browser ASLR bypasses, though signatures must be validated for this specific CVE.
• Feature disablement: Where group policy permits, disable Internet Explorer entirely or restrict it to trusted zones and intranet sites only. Turn off unnecessary scripting and ActiveX in the Internet and Restricted Sites zones.
• Heightened monitoring: Alert on iexplore.exe spawning unusual child processes, loading unsigned modules, or making atypical network connections. Retain browser crash dumps for later analysis.

Revisit the exception regularly; compensating controls are temporary.

If your data may have been exposed

Actively exploited browser vulnerabilities frequently serve as the initial vector for credential theft, ransomware, or further lateral movement, although ransomware use specifically tied to CVE-2015-0071 is not documented in the provided facts. If you have reason to believe systems were compromised while unpatched, follow your incident-response plan: isolate hosts, collect forensic images, reset credentials, and hunt for persistence. As a quick additional check, users can run a free exposure scan of their work email addresses against known breach data sets to see whether those identities already appear in public dumps.