CVE-2015-1635 in Windows
Summary
by MITRE
HTTP.sys in Microsoft Windows 7 SP1, Windows Server 2008 R2 SP1, Windows 8, Windows 8.1, and Windows Server 2012 Gold and R2 allows remote attackers to execute arbitrary code via crafted HTTP requests, aka "HTTP.sys Remote Code Execution Vulnerability."
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Analysis
by VulDB Data Team • 04/22/2026
The CVE-2015-1635 vulnerability represents a critical remote code execution flaw in the HTTP.sys kernel driver of Microsoft Windows operating systems. This vulnerability specifically affects Windows 7 SP1, Windows Server 2008 R2 SP1, Windows 8, Windows 8.1, and Windows Server 2012 Gold and R2 versions. The flaw resides in the HTTP protocol stack implementation within the kernel mode component, making it particularly dangerous as it can be exploited without authentication from remote attackers. The vulnerability was extensively analyzed by security researchers and became widely known as the "HTTP.sys Remote Code Execution Vulnerability" due to its ability to allow attackers to execute arbitrary code on affected systems. This issue stems from improper validation of HTTP requests within the kernel-level HTTP.sys driver, which processes incoming HTTP traffic and handles various HTTP protocol operations including range requests and other header processing functions.
The technical exploitation of this vulnerability occurs through specifically crafted HTTP requests that trigger a buffer overflow condition within the HTTP.sys driver. When the driver processes malformed HTTP headers, particularly those containing crafted range requests or other HTTP header values, it fails to properly validate input parameters before processing them. This validation failure leads to memory corruption that can be leveraged by attackers to execute arbitrary code with kernel-level privileges. The vulnerability is particularly concerning because it operates at the kernel level, meaning successful exploitation grants attackers complete control over the affected system. The flaw is categorized under CWE-121, which describes "Stack-based Buffer Overflow" conditions, though the specific implementation involves kernel memory corruption rather than traditional stack-based issues. Attackers can craft HTTP requests that cause the driver to write beyond allocated buffer boundaries, potentially allowing for code execution in kernel space.
The operational impact of CVE-2015-1635 extends beyond individual system compromise to potentially enable large-scale attacks across networks. Since the vulnerability affects core Windows components and can be exploited remotely without authentication, it provides attackers with a powerful vector for lateral movement and persistent access within networks. Once an attacker gains kernel-level access through this vulnerability, they can escalate privileges, install backdoors, modify system files, and establish persistence mechanisms. The vulnerability's exploitation can lead to complete system compromise, data exfiltration, and further network infiltration. Organizations running affected Windows versions are particularly vulnerable because the flaw affects widely deployed server and desktop operating systems, making it a prime target for automated exploitation campaigns. The vulnerability's presence in multiple Windows versions means that organizations must assess their entire infrastructure for potential exposure, as any system running the affected operating systems remains at risk.
Microsoft addressed this vulnerability through the release of security update MS15-034, which patched the HTTP.sys driver to properly validate incoming HTTP requests and prevent the buffer overflow conditions that enabled exploitation. Organizations should prioritize immediate deployment of this security update across all affected systems to mitigate the risk. Additional mitigations include implementing network-based restrictions such as blocking HTTP traffic at perimeter firewalls, disabling unnecessary HTTP services, and monitoring for suspicious HTTP request patterns. The vulnerability's classification under the ATT&CK framework falls under the "Execution" and "Persistence" tactics, as exploitation enables arbitrary code execution followed by potential persistence mechanisms. Network administrators should also consider implementing intrusion detection systems that can identify and block the specific HTTP request patterns associated with this vulnerability. The incident highlighted the importance of kernel-level security and the need for robust input validation in system drivers, as even minor validation flaws in core components can lead to severe security consequences affecting millions of systems worldwide.