CVE-2012-6036 in Xen
Summary
by MITRE
The (1) memc_save_get_next_page, (2) tmemc_restore_put_page and (3) tmemc_restore_flush_page functions in the Transcendent Memory (TMEM) in Xen 4.0, 4.1, and 4.2 do not check for negative id pools, which allows local guest OS users to cause a denial of service (memory corruption and host crash) or possibly execute arbitrary code via unspecified vectors. NOTE: this issue was originally published as part of CVE-2012-3497, which was too general; CVE-2012-3497 has been SPLIT into this ID and others.
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Analysis
by VulDB Data Team • 12/20/2021
The vulnerability described in CVE-2012-6036 resides within the Transcendent Memory (TMEM) subsystem of the Xen hypervisor version 4.0, 4.1, and 4.2, representing a critical security flaw that affects virtual machine environments. This issue specifically targets three distinct functions: memc_save_get_next_page, tmemc_restore_put_page, and tmemc_restore_flush_page, all of which operate within the TMEM framework designed to provide memory management capabilities across virtualized environments. The flaw manifests when these functions fail to validate id pool parameters, creating a potential attack surface that can be exploited by local users within guest operating systems to compromise host system integrity.
The technical root cause of this vulnerability stems from inadequate input validation within the TMEM subsystem where negative id pool values are not properly checked before processing. This absence of validation creates a condition where malicious or malformed input can be passed through the memory management functions, leading to unpredictable behavior in the hypervisor's memory handling mechanisms. According to CWE classification, this represents a weakness in input validation where negative values are not properly constrained, falling under CWE-20: Improper Input Validation. The lack of proper bounds checking and parameter validation allows attackers to manipulate memory allocation and deallocation processes, potentially causing memory corruption within the hypervisor's address space.
The operational impact of this vulnerability extends beyond simple denial of service, presenting potential for arbitrary code execution within the host system. Local guest OS users who can access the affected functions can exploit this flaw to trigger memory corruption that may result in system crashes, data loss, or more severe consequences including privilege escalation. The vulnerability's potential for remote code execution makes it particularly dangerous in multi-tenant virtualized environments where guest users might attempt to compromise other virtual machines or the underlying host infrastructure. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and execution through hypervisor manipulation, specifically targeting the T1059.007 technique for command and script injection within virtualized environments.
Mitigation strategies for CVE-2012-6036 require immediate patching of affected Xen hypervisor versions, with administrators prioritizing updates to versions that contain proper input validation for id pool parameters. System administrators should implement monitoring for unusual memory allocation patterns and host system instability that might indicate exploitation attempts. The fix typically involves adding proper validation checks to ensure id pool values remain within acceptable ranges before processing, preventing negative values from being passed to memory management functions. Additionally, organizations should consider implementing network segmentation and access controls to limit guest user privileges and reduce the potential attack surface. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other hypervisor components, as this vulnerability demonstrates the importance of proper input validation in critical system components. The remediation process should also include thorough testing of patched systems to ensure that the vulnerability is fully resolved without introducing regressions in system functionality.