CVE-2017-5898 in QEMU
Summary
by MITRE
Integer overflow in the emulated_apdu_from_guest function in usb/dev-smartcard-reader.c in Quick Emulator (Qemu), when built with the CCID Card device emulator support, allows local users to cause a denial of service (application crash) via a large Application Protocol Data Units (APDU) unit.
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Analysis
by VulDB Data Team • 09/08/2020
The vulnerability identified as CVE-2017-5898 represents a critical integer overflow flaw within the Quick Emulator QEMU software stack, specifically affecting systems that utilize the CCID Card device emulator functionality. This issue manifests in the emulated_apdu_from_guest function located in the usb/dev-smartcard-reader.c source file, where improper handling of Application Protocol Data Units (APDUs) creates a pathway for malicious exploitation. The vulnerability occurs exclusively when QEMU is compiled with CCID Card device support, making it relevant to virtualization environments that incorporate smart card emulation capabilities. The flaw demonstrates a classic software engineering oversight where arithmetic operations fail to properly validate input parameters, leading to unexpected behavior when processing oversized data structures.
The technical exploitation of this vulnerability hinges on the manipulation of APDU data structures that exceed the capacity of integer variables used in the processing logic. When a local user submits a large APDU unit to the emulated smartcard reader, the integer overflow condition causes the application to behave unpredictably, ultimately resulting in a crash of the QEMU process. This type of vulnerability falls under CWE-190, which specifically addresses integer overflow conditions that can lead to buffer overflows and application instability. The flaw demonstrates how improper input validation can create cascading failures in virtualized environments where multiple system components interact through well-defined interfaces. The CCID (Chip Card Interface Device) protocol implementation within QEMU's smartcard reader emulation creates a specific attack surface where malicious APDU data can trigger the overflow condition during data processing.
The operational impact of CVE-2017-5898 extends beyond simple denial of service, as it represents a potential vector for more sophisticated attacks within virtualized environments. A successful exploitation can disrupt critical virtual machine operations, particularly in scenarios where smart card authentication is required for secure access control. The vulnerability affects organizations using QEMU for desktop virtualization, server consolidation, or security testing environments where smart card readers are emulated for compatibility purposes. From an attack perspective, this flaw aligns with ATT&CK technique T1059.001, which involves the use of command and scripting interpreters, as local users can leverage the overflow to cause system instability. The vulnerability particularly impacts enterprise environments where virtual machines may be configured with smart card reader emulators for authentication purposes, creating opportunities for both accidental and intentional disruption of critical services.
Mitigation strategies for CVE-2017-5898 should prioritize immediate patching of affected QEMU installations, as the vulnerability exists in the core emulation logic of the software. Organizations should disable CCID Card device support in QEMU configurations when this functionality is not required, effectively removing the attack surface. System administrators should implement monitoring protocols to detect unusual APDU processing patterns that might indicate exploitation attempts. The vulnerability highlights the importance of input validation and proper integer handling in virtualization software, as similar issues could exist in other components of the QEMU codebase. Security teams should conduct comprehensive audits of virtualization environments to identify all instances where smart card emulation is enabled, particularly in systems handling sensitive data or requiring high availability. Additionally, implementing network segmentation and access controls can limit the potential impact of local exploitation attempts, while regular security assessments should verify that patched versions are properly deployed across all virtualization infrastructure.