CVE-2017-6414 in libcacard
Summary
by MITRE
Memory leak in the vcard_apdu_new function in card_7816.c in libcacard before 2.5.3 allows local guest OS users to cause a denial of service (host memory consumption) via vectors related to allocating a new APDU object.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability described in CVE-2017-6414 represents a critical memory management flaw within the libcacard library, specifically affecting versions prior to 2.5.3. This issue resides in the vcard_apdu_new function located in the card_7816.c source file, which governs the allocation and management of APDU (Application Protocol Data Unit) objects within smart card communication frameworks. The flaw manifests as a memory leak that occurs during the creation of new APDU objects, creating a condition where allocated memory is not properly released back to the system. This vulnerability is particularly concerning because it exists within the context of virtualized environments where guest operating systems interact with host systems through smart card emulation mechanisms, making it exploitable by local users within the guest environment.
The technical implementation of this vulnerability stems from improper memory deallocation practices within the vcard_apdu_new function, which is responsible for initializing new APDU objects for smart card communication protocols. When a guest OS user executes operations that trigger the creation of new APDU objects, the function allocates memory for these structures but fails to maintain proper cleanup routines. This memory leak accumulates over time as multiple APDU objects are created without corresponding deallocation, leading to progressive host memory consumption. The vulnerability operates at the intersection of virtualization security and smart card emulation, where the guest OS can leverage this flaw to exhaust available memory resources on the host system through repeated allocation requests. The flaw aligns with CWE-401: Improper Release of Memory and represents a classic case of resource exhaustion that can be exploited to cause system instability.
From an operational impact perspective, this vulnerability enables local guest OS users to execute a denial of service attack against the host system by consuming excessive memory resources. The memory leak directly translates to reduced system performance and potential system crashes when host memory becomes exhausted, affecting not only the virtualized environment but potentially impacting other running services and applications on the same host. The attack vector is particularly insidious because it requires minimal privileges within the guest environment and can be executed repeatedly to amplify the memory consumption effect. This vulnerability is especially dangerous in multi-tenant virtualization environments where one compromised guest could potentially affect the entire host system and other virtual machines running on the same physical hardware. The impact extends beyond simple resource exhaustion to include potential service disruption and system availability issues that could affect business operations.
Mitigation strategies for CVE-2017-6414 should prioritize immediate patching of affected libcacard versions to 2.5.3 or later, which contains the necessary memory management fixes. System administrators should implement monitoring solutions to detect unusual memory consumption patterns that could indicate exploitation attempts, particularly in virtualized environments where guest-to-host communication is prevalent. Network segmentation and access controls should be strengthened to limit guest OS privileges and reduce the attack surface available to potential exploiters. Additionally, implementing memory usage limits and resource quotas for virtual machines can help contain the impact of such memory leaks. The vulnerability demonstrates the importance of proper memory management practices in security-critical components and aligns with ATT&CK technique T1499.001: Endpoint Denial of Service, which emphasizes the need for robust resource management in virtualized environments. Organizations should also conduct regular security assessments of their virtualization infrastructure to identify similar memory management flaws that could be exploited for similar denial of service attacks.