CVE-2011-1965 in Windows
Summary
by MITRE
Tcpip.sys in the TCP/IP stack in Microsoft Windows 7 Gold and SP1 and Windows Server 2008 R2 and R2 SP1 does not properly implement URL-based QoS, which allows remote attackers to cause a denial of service (reboot) via a crafted URL to a web server, aka "TCP/IP QOS Denial of Service Vulnerability."
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Analysis
by VulDB Data Team • 03/16/2025
The vulnerability identified as CVE-2011-1965 resides within the Tcpip.sys driver component of Microsoft Windows operating systems, specifically affecting Windows 7 Gold and SP1 versions along with Windows Server 2008 R2 and R2 SP1 releases. This issue stems from improper implementation of Quality of Service (QoS) functionality within the TCP/IP networking stack, creating a significant security weakness that can be exploited remotely. The flaw manifests when a maliciously crafted URL is processed by a web server, leading to a system reboot and subsequent denial of service condition that compromises the availability of critical network services.
The technical root cause of this vulnerability lies in the flawed handling of URL-based QoS parameters within the kernel-mode Tcpip.sys driver. When a web server processes a specially crafted URL containing malformed QoS specifications, the system fails to properly validate or sanitize these parameters before processing them within the network stack. This improper input validation creates a condition where the TCP/IP subsystem becomes vulnerable to memory corruption or resource exhaustion, ultimately leading to system instability and forced reboot operations. The vulnerability operates at the kernel level, making it particularly dangerous as it can be triggered without requiring elevated privileges and can affect any system running the vulnerable operating systems.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged to cause complete system disruption across networked environments. Attackers can exploit this weakness by crafting malicious URLs that, when accessed through web browsers or web server applications, trigger the vulnerable code path in Tcpip.sys. The resulting system reboot not only interrupts legitimate network services but can also potentially disrupt critical business operations, especially in environments where continuous availability is essential. This vulnerability particularly affects enterprise environments where web servers and network infrastructure are exposed to external traffic, as it provides a straightforward method for causing widespread service disruption without requiring sophisticated attack vectors or privileged access.
Mitigation strategies for CVE-2011-1965 should prioritize immediate patch deployment through Microsoft's security updates, as the vulnerability has been addressed in subsequent security releases. Organizations should implement network segmentation and access controls to limit exposure of vulnerable systems to untrusted traffic sources, while also monitoring network traffic for suspicious URL patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and relates to ATT&CK technique T1499.004 for network denial of service attacks. Additionally, implementing proper input validation mechanisms at application layers and maintaining updated security monitoring solutions can help detect and prevent exploitation attempts, while regular security assessments should verify that systems remain protected against similar vulnerabilities in the TCP/IP stack implementation.