CVE-2011-4111 in QEMU
Summary
by MITRE
Buffer overflow in the ccid_card_vscard_handle_message function in hw/ccid-card-passthru.c in QEMU before 0.15.2 and 1.x before 1.0-rc4 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted VSC_ATR message.
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Analysis
by VulDB Data Team • 04/12/2025
The vulnerability described in CVE-2011-4111 represents a critical buffer overflow flaw within the QEMU virtualization platform's smart card passthrough functionality. This issue exists in the ccid_card_vscard_handle_message function located in the hw/ccid-card-passthru.c source file, affecting QEMU versions prior to 0.15.2 and 1.x versions before 1.0-rc4. The vulnerability specifically targets the handling of VSC_ATR messages, which are used in smart card communication protocols to transmit card identification information. The buffer overflow occurs when the system processes malformed or specially crafted VSC_ATR messages, creating a potential attack vector that could be exploited by remote adversaries.
The technical nature of this vulnerability stems from inadequate input validation and bounds checking within the smart card communication handler. When a maliciously crafted VSC_ATR message is received, the function fails to properly verify the message length against the allocated buffer space, leading to memory corruption. This buffer overflow condition can result in unpredictable behavior including program crashes, memory corruption, and potentially arbitrary code execution within the QEMU process context. The flaw is classified as a classic stack-based buffer overflow under CWE-121, which occurs when a program writes data beyond the boundaries of a fixed-length buffer, potentially overwriting adjacent memory locations including return addresses and function pointers.
The operational impact of this vulnerability extends beyond simple denial of service, as it creates opportunities for remote code execution within the virtualization environment. Attackers could leverage this flaw to compromise the integrity of virtual machines running on affected QEMU installations, potentially leading to privilege escalation or complete system compromise depending on the execution context. The vulnerability affects virtualized environments where smart card passthrough functionality is enabled, making it particularly dangerous in enterprise settings where QEMU is used for virtual desktop infrastructure or secure application deployment. This issue aligns with ATT&CK technique T1059.007 for remote code execution through virtualization environments and represents a significant risk to organizations relying on QEMU for virtualization services.
Mitigation strategies for CVE-2011-4111 primarily involve immediate patching of affected QEMU installations to versions 0.15.2 or 1.0-rc4 and later, which contain the necessary fixes for the buffer overflow condition. Organizations should also implement network segmentation to limit access to virtualization management interfaces and disable unnecessary smart card passthrough features when not required. Additional defensive measures include monitoring for suspicious VSC_ATR message patterns and implementing intrusion detection systems that can identify malformed smart card communication attempts. The vulnerability demonstrates the importance of input validation in virtualization components and highlights the need for comprehensive security testing of device emulation code within hypervisor environments. System administrators should also consider implementing privilege separation and sandboxing techniques to limit the potential impact of successful exploitation attempts.