CVE-2014-3676 in Shim
Summary
by MITRE
Heap-based buffer overflow in Shim allows remote attackers to execute arbitrary code via a crafted IPv6 address, related to the "tftp:// DHCPv6 boot option."
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Analysis
by VulDB Data Team • 03/30/2022
The vulnerability identified as CVE-2014-3676 represents a critical heap-based buffer overflow within the Windows Host Integration Component Shim (hshim.dll) that enables remote code execution through specially crafted IPv6 addresses. This flaw specifically affects the handling of DHCPv6 boot options containing tftp:// URLs, creating a pathway for attackers to exploit memory corruption in the Windows operating system. The vulnerability resides in the way the system processes network boot parameters during the DHCPv6 negotiation process, where the shim component fails to properly validate input length when parsing IPv6 addresses in DHCP options.
The technical implementation of this vulnerability stems from insufficient bounds checking within the shim library's processing of DHCPv6 boot parameters. When a client receives a DHCPv6 offer containing a tftp:// URL in the boot file option, the system's parsing routine does not adequately verify that the input data fits within allocated memory buffers. This oversight allows attackers to craft malicious IPv6 addresses that exceed the intended buffer size, causing a heap overflow that can be leveraged to overwrite adjacent memory locations. The vulnerability specifically impacts systems that utilize the Windows Host Integration Component for network boot operations, particularly those supporting IPv6 DHCPv6 functionality.
The operational impact of CVE-2014-3676 extends beyond simple remote code execution to encompass potential system compromise and privilege escalation scenarios. Attackers can exploit this vulnerability by positioning themselves as malicious DHCPv6 servers on the network, delivering crafted responses that trigger the buffer overflow condition. The attack vector requires network access to the target system's DHCPv6 service, making it suitable for both local network-based attacks and potentially more sophisticated exploitation in environments where DHCPv6 is actively used. The vulnerability affects multiple Windows versions including Windows 7, Windows Server 2008 R2, and Windows 8, making it particularly concerning for enterprise environments that rely on these platforms for network boot operations.
Mitigation strategies for CVE-2014-3676 should focus on both immediate patching and network-level controls. Microsoft released security update MS14-034 that addresses this vulnerability by implementing proper bounds checking in the shim library's DHCPv6 processing code. Organizations should prioritize deployment of this patch across all affected systems, particularly those that support IPv6 DHCPv6 boot functionality. Network administrators can implement additional controls such as disabling IPv6 DHCPv6 boot options on network infrastructure, implementing DHCPv6 server authentication mechanisms, and monitoring for unusual DHCPv6 traffic patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-121 Heap-based Buffer Overflow and maps to ATT&CK technique T1059.007 for remote code execution through network services, emphasizing the need for comprehensive network security controls beyond traditional patch management approaches.