CVE-2017-14316 in Xen
Summary
by MITRE
A parameter verification issue was discovered in Xen through 4.9.x. The function `alloc_heap_pages` allows callers to specify the first NUMA node that should be used for allocations through the `memflags` parameter; the node is extracted using the `MEMF_get_node` macro. While the function checks to see if the special constant `NUMA_NO_NODE` is specified, it otherwise does not handle the case where `node >= MAX_NUMNODES`. This allows an out-of-bounds access to an internal array.
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Analysis
by VulDB Data Team • 01/11/2021
The vulnerability identified as CVE-2017-14316 represents a critical memory safety issue within the Xen hypervisor version 4.9.x and earlier. This flaw exists in the memory allocation subsystem where the `alloc_heap_pages` function processes memory allocation requests through the `memflags` parameter. The function utilizes the `MEMF_get_node` macro to extract NUMA node information from the memory flags, creating a pathway for potential exploitation through improper parameter validation. The vulnerability stems from insufficient bounds checking on the node identifier value, specifically failing to validate that the extracted node number remains within acceptable limits defined by the system's maximum NUMA node configuration.
The technical implementation of this vulnerability occurs when an attacker provides a malicious `memflags` parameter containing a node value that exceeds the `MAX_NUMNODES` constant defined within the Xen hypervisor. While the code properly handles the special `NUMA_NO_NODE` constant, it neglects to validate that node identifiers fall within the valid range of 0 to MAX_NUMNODES-1. This omission creates a scenario where the hypervisor attempts to access an internal array using an out-of-bounds index, leading to potential memory corruption or unauthorized data access. The flaw manifests as an integer overflow or underflow condition that bypasses the normal bounds checking mechanisms, allowing arbitrary memory access patterns.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a potential privilege escalation vector within the hypervisor environment. Attackers could leverage this issue to manipulate memory allocation decisions across NUMA nodes, potentially compromising the integrity of memory management operations. The vulnerability aligns with CWE-129, which addresses insufficient validation of length of inputs, and CWE-787, which covers out-of-bounds write operations. From an ATT&CK perspective, this vulnerability maps to T1068, which involves exploiting legitimate credentials or privileges, and could enable techniques for privilege escalation or system compromise within virtualized environments.
Mitigation strategies for CVE-2017-14316 require immediate patch application from Xen maintainers, as the vulnerability exists in versions through 4.9.x. Organizations should implement comprehensive monitoring of hypervisor memory allocation patterns and establish strict parameter validation controls. The fix typically involves adding proper bounds checking to ensure that node identifiers remain within the valid range before processing, preventing the out-of-bounds array access. System administrators should also consider implementing memory access controls and privilege separation measures to limit the potential impact of such vulnerabilities. Additionally, regular security assessments of virtualization environments should include checks for similar parameter validation flaws, as this represents a common pattern in hypervisor security that may affect other memory management functions. The vulnerability demonstrates the critical importance of validating all user-provided parameters in kernel and hypervisor code, particularly in systems where memory management directly impacts overall system stability and security.