CVE-2017-16845 in QEMU
Summary
by MITRE
hw/input/ps2.c in Qemu does not validate 'rptr' and 'count' values during guest migration, leading to out-of-bounds access.
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Analysis
by VulDB Data Team • 01/10/2023
The vulnerability identified as CVE-2017-16845 resides within the QEMU hypervisor's input subsystem, specifically in the ps2.c file responsible for handling PS/2 keyboard and mouse input devices. This flaw represents a critical validation issue that occurs during the guest migration process, where QEMU fails to properly validate the 'rptr' and 'count' parameters associated with input device state management. The absence of proper boundary checking creates a scenario where malicious or malformed input data could be processed without adequate safeguards, potentially leading to memory corruption and system instability.
The technical implementation of this vulnerability stems from the migration protocol handling within QEMU's PS/2 device emulation layer. During migration operations, the hypervisor must serialize and deserialize the state of input devices to maintain consistent functionality across host systems. The 'rptr' parameter typically represents a read pointer for input buffers while 'count' indicates the number of elements in the buffer. When these values are not validated during migration, an attacker can manipulate these parameters to reference memory locations outside the intended buffer boundaries, creating conditions for out-of-bounds memory access. This type of vulnerability falls under the CWE-129 weakness category, specifically addressing insufficient input validation and improper boundary checking in input processing.
The operational impact of this vulnerability extends beyond simple memory corruption, as it could potentially enable privilege escalation or denial of service conditions within virtualized environments. When a malicious guest operating system or hypervisor-level attack manipulates the 'rptr' and 'count' values during migration, it may trigger memory access violations that could be exploited to execute arbitrary code or cause system crashes. The vulnerability affects QEMU versions prior to 2.11.0, making it particularly concerning for environments that rely on older hypervisor implementations. Attackers could leverage this weakness to compromise the integrity of the virtualization layer, potentially affecting multiple guest operating systems running on the same host. This aligns with ATT&CK technique T1059.001 for command and scripting interpreter, as exploitation may involve crafting malicious input sequences to trigger the out-of-bounds access condition.
Mitigation strategies for CVE-2017-16845 primarily focus on updating QEMU installations to versions 2.11.0 or later, where proper validation of 'rptr' and 'count' parameters has been implemented. Administrators should also consider implementing network segmentation and access controls to limit exposure during migration operations. The fix involves adding comprehensive validation checks to ensure that the read pointer and count values remain within valid buffer boundaries before processing migration data. Additionally, organizations should conduct regular vulnerability assessments of their virtualization infrastructure and implement monitoring solutions to detect anomalous migration patterns that could indicate exploitation attempts. The remediation process should include thorough testing of migration workflows to ensure that the validation changes do not introduce performance regressions or compatibility issues with existing virtual environments.