CVE-2018-17963 in QEMU
Summary
by MITRE
qemu_deliver_packet_iov in net/net.c in Qemu accepts packet sizes greater than INT_MAX, which allows attackers to cause a denial of service or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 05/23/2023
The vulnerability identified as CVE-2018-17963 resides within the QEMU virtualization platform's network subsystem, specifically in the qemu_deliver_packet_iov function located in net/net.c. This flaw represents a classic integer overflow condition that occurs when processing network packets, where the system fails to properly validate packet sizes before processing them. The vulnerability manifests when QEMU receives packets that exceed the maximum value representable by a signed 32-bit integer, commonly known as INT_MAX, which is 2,147,483,647 bytes. When packet sizes surpass this threshold, the system's internal handling mechanisms become compromised, potentially leading to critical system instability.
The technical nature of this vulnerability stems from inadequate input validation within the network packet processing pipeline of QEMU's virtual network interface. The qemu_deliver_packet_iov function is responsible for delivering network packets to virtual machines through various network backends including tap interfaces, user networking, and others. When an attacker crafts malicious network packets with sizes exceeding INT_MAX, the system's internal integer arithmetic operations become corrupted, leading to unpredictable behavior. This condition can trigger buffer overflows, memory corruption, or other low-level system failures that ultimately result in denial of service conditions. The vulnerability is particularly concerning because it can be exploited without requiring elevated privileges, making it accessible to remote attackers who can manipulate network traffic.
From an operational perspective, this vulnerability presents significant risks to virtualized environments where QEMU serves as the primary hypervisor platform. The denial of service impact can render virtual machines unavailable, effectively disrupting services that depend on virtualized infrastructure. In environments where multiple virtual machines are running simultaneously, a successful exploitation could cascade into broader system failures, potentially affecting entire virtualized data centers. The unspecified other impacts mentioned in the CVE description suggest that beyond simple denial of service, attackers might potentially leverage this condition to execute arbitrary code or escalate privileges, though the exact attack vectors remain undetermined. The vulnerability affects various QEMU versions and can be exploited through any network interface that utilizes the affected packet delivery mechanism.
Mitigation strategies for CVE-2018-17963 should focus on implementing proper input validation and bounds checking within the QEMU network subsystem. System administrators should immediately upgrade to patched versions of QEMU where the integer overflow has been addressed through proper size validation before packet processing. The fix typically involves adding checks to ensure packet sizes do not exceed maximum integer limits before proceeding with network packet delivery operations. Additionally, network segmentation and access controls should be implemented to limit exposure to potentially malicious network traffic. Monitoring systems should be configured to detect unusual packet sizes that might indicate exploitation attempts. Organizations running QEMU-based virtualization environments should also consider implementing network intrusion detection systems that can identify and block packets with suspiciously large sizes. This vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and can be mapped to ATT&CK technique T1059.007 for command and script injection through network-based attacks. The security community should also implement regular security assessments and penetration testing to identify similar vulnerabilities in other virtualization components that might present analogous integer overflow conditions.