CVE-2018-20123 in QEMU
Summary
by MITRE
pvrdma_realize in hw/rdma/vmw/pvrdma_main.c in QEMU has a Memory leak after an initialisation error.
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability identified as CVE-2018-20123 resides within the QEMU virtualization platform's RDMA implementation, specifically in the pvrdma_realize function located at hw/rdma/vmw/pvrdma_main.c. This memory leak occurs during the initialization phase of the pvrdma device, representing a critical flaw that can significantly impact system stability and resource management within virtualized environments. The issue manifests when the device initialization process encounters an error condition, yet fails to properly release allocated memory resources before terminating the initialization sequence.
The technical flaw stems from inadequate error handling within the pvrdma_realize function where memory allocations occur during device setup but are not consistently freed when initialization fails. This represents a classic memory management issue that aligns with CWE-401, which specifically addresses improper deallocation of memory resources. The vulnerability is particularly concerning because it affects the hypervisor layer where QEMU operates as a virtual machine monitor, potentially allowing malicious actors to exploit resource exhaustion conditions that could lead to denial of service attacks against virtualized systems.
From an operational impact perspective, this memory leak can accumulate over time as multiple initialization attempts occur, particularly in environments where virtual machines are frequently created and destroyed. The vulnerability affects systems running QEMU versions prior to the patched release, making it relevant to enterprise virtualization deployments, cloud infrastructure providers, and any organization utilizing QEMU-based virtualization solutions. The memory consumption grows with each failed initialization attempt, potentially leading to system instability or complete resource exhaustion that could affect other virtual machines sharing the same host resources.
The exploitation of this vulnerability requires an attacker to trigger the specific error condition during device initialization, which could occur through malformed device configuration or attempted privilege escalation attempts. This aligns with ATT&CK technique T1059, which involves executing commands through various interfaces, as attackers may attempt to manipulate virtual device configurations to trigger the memory leak condition. The vulnerability's impact is amplified in multi-tenant environments where resource exhaustion could affect other virtual machines on the same host system, potentially enabling cross-tenant resource contention attacks.
Mitigation strategies should prioritize updating QEMU to versions that contain the specific patch addressing this memory leak issue, as provided by the vendor's security advisory. Organizations should also implement monitoring solutions to detect anomalous memory usage patterns that could indicate exploitation attempts. Additionally, virtualization administrators should review and harden device initialization processes, implementing proper error handling mechanisms and resource cleanup procedures to prevent similar issues in custom or third-party QEMU implementations. The patch for this vulnerability typically includes proper memory deallocation routines that execute regardless of initialization success or failure, ensuring that all allocated resources are consistently freed when the device initialization process terminates.