CVE-2011-1869 in Windows
Summary
by MITRE
The Distributed File System (DFS) implementation in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, R2, and R2 SP1, and Windows 7 Gold and SP1 allows remote DFS servers to cause a denial of service (system hang) via a crafted referral response, aka "DFS Referral Response Vulnerability."
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Analysis
by VulDB Data Team • 11/09/2021
The CVE-2011-1869 vulnerability represents a critical denial of service flaw within Microsoft's Distributed File System implementation across multiple operating system versions. This vulnerability specifically targets the DFS referral response mechanism that enables clients to locate and access network resources through a hierarchical naming structure. The flaw exists in the way Windows systems process DFS referral responses from remote servers, creating a condition where malformed or specially crafted responses can trigger system instability. The vulnerability affects a broad range of Microsoft operating systems including Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, R2, and R2 SP1, as well as Windows 7 Gold and SP1, making it particularly concerning for enterprise environments with diverse operating system deployments. This vulnerability falls under the CWE-129 weakness category, which encompasses improper validation of input boundaries, and aligns with ATT&CK technique T1499.004 for network denial of service attacks.
The technical exploitation of this vulnerability occurs when a remote DFS server responds to a client request with a maliciously crafted referral packet. The DFS client implementation fails to properly validate the structure and content of these referral responses, allowing an attacker to construct responses that cause the client system to enter an infinite loop or consume excessive system resources. When the vulnerable system processes such a malformed referral, it can result in a complete system hang or crash, effectively rendering the affected machine unusable until manual intervention or system reboot occurs. The vulnerability specifically targets the DFS client service (dfs.exe) and related system components that handle the distributed file system protocols, making it particularly dangerous in networked environments where DFS is actively used for resource sharing and access control.
The operational impact of CVE-2011-1869 extends beyond simple system unavailability, as it can disrupt business operations across entire network segments that rely on DFS for file access and resource sharing. Organizations with extensive DFS deployments may experience cascading failures where a single compromised or malicious DFS server can bring down multiple client systems simultaneously. This vulnerability is particularly dangerous in enterprise environments where DFS is used for centralized file server access, domain controller replication, or backup and recovery operations. The attack vector requires minimal privileges and can be executed remotely, making it an attractive target for both malicious actors and automated exploitation tools. Network administrators face significant challenges in detecting and mitigating this vulnerability due to its subtle nature and the widespread use of DFS across various system architectures.
Mitigation strategies for CVE-2011-1869 should focus on both immediate patch deployment and network-level controls. Microsoft released security updates through Windows Update and Microsoft Download Center that address this vulnerability by implementing proper validation of DFS referral responses. Organizations should prioritize patching all affected systems, particularly those running older operating systems like Windows XP and Windows Server 2003 that are no longer receiving mainstream support. Network segmentation and firewall rules can help limit the exposure by restricting DFS traffic between trusted network segments. Implementing monitoring solutions to detect unusual DFS referral patterns and system behavior can provide early warning of potential exploitation attempts. Additionally, organizations should consider disabling DFS functionality on systems where it is not essential, and implement proper network access controls to prevent unauthorized DFS server access. The vulnerability demonstrates the importance of maintaining up-to-date security patches and the risks associated with legacy system support in enterprise environments.