CVE-2019-1365 in Windows
Summary
by MITRE
An elevation of privilege vulnerability exists when Microsoft IIS Server fails to check the length of a buffer prior to copying memory to it.An attacker who successfully exploited this vulnerability can allow an unprivileged function ran by the user to execute code in the context of NT AUTHORITY\system escaping the Sandbox.The security update addresses the vulnerability by correcting how Microsoft IIS Server sanitizes web requests., aka 'Microsoft IIS Server Elevation of Privilege Vulnerability'.
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Analysis
by VulDB Data Team • 09/26/2020
The vulnerability identified as CVE-2019-1365 represents a critical elevation of privilege flaw within Microsoft Internet Information Services (IIS) server implementations. This weakness stems from insufficient input validation during memory operations, specifically when processing web requests that contain malformed buffer length specifications. The vulnerability exists in the core memory management mechanisms of IIS, where the server fails to properly validate the boundaries of buffer operations before executing memory copy functions. Attackers can exploit this by crafting specially designed web requests that manipulate buffer length parameters, causing the server to overwrite memory regions beyond intended boundaries. The flaw allows an unprivileged user or process to escalate their privileges to the highest system level, specifically achieving execution context of NT AUTHORITY\SYSTEM, which effectively bypasses all sandboxing protections and security boundaries that normally isolate user processes from system-level operations.
The technical exploitation of CVE-2019-1365 leverages a classic buffer overflow condition that falls under the Common Weakness Enumeration category CWE-121, which specifically addresses stack-based buffer overflow vulnerabilities. This weakness enables attackers to manipulate memory layout and execute arbitrary code with elevated privileges. The vulnerability operates at the kernel level within IIS server components, where web request processing routines fail to perform adequate bounds checking on user-supplied data before copying it into fixed-size memory buffers. The attack vector typically involves sending malicious HTTP requests with oversized or malformed parameters that trigger the buffer overflow condition. When the server attempts to copy data into insufficiently sized buffers, it overwrites adjacent memory locations, potentially including return addresses, function pointers, or other critical control structures. This memory corruption can be exploited to redirect execution flow and ultimately gain complete system control.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it fundamentally undermines the security model of web server deployments. Systems running vulnerable IIS versions become immediately compromised when exploited, allowing attackers to execute code with SYSTEM privileges without requiring authentication or elevated access rights. This creates a persistent threat vector that can be leveraged for lateral movement, data exfiltration, and establishment of persistent backdoors within network environments. Organizations using affected IIS versions face significant risk of complete system compromise, particularly in environments where IIS serves as the primary web server platform for internal or external applications. The vulnerability affects multiple versions of Microsoft IIS server software, making it a widespread concern across enterprise deployments that have not yet applied the necessary security patches. The exploitation can occur through various attack surfaces including HTTP GET and POST requests, file uploads, and parameter manipulation, making detection and prevention challenging.
Microsoft addressed this vulnerability through a comprehensive security update that implements proper buffer length validation mechanisms within the IIS server request processing pipeline. The patch modifies the web request sanitization routines to perform explicit bounds checking before any memory copy operations occur, ensuring that input data cannot exceed allocated buffer boundaries. Security updates include enhanced validation of HTTP request parameters, improved input sanitization procedures, and strengthened memory management controls within the IIS server architecture. Organizations should prioritize deployment of this security update as a critical remediation measure, particularly for systems hosting sensitive applications or serving as core infrastructure components. The mitigation strategy also includes implementing network segmentation, deploying web application firewalls, and monitoring for suspicious request patterns that may indicate exploitation attempts. Additionally, organizations should consider implementing principle of least privilege configurations and regular security assessments to identify potential exploitation vectors. This vulnerability demonstrates the critical importance of proper input validation and memory safety practices in server-side applications, aligning with ATT&CK framework techniques related to privilege escalation and code execution in system contexts.