CVE-2017-15119 in QEMU
Summary
by MITRE
The Network Block Device (NBD) server in Quick Emulator (QEMU) before 2.11 is vulnerable to a denial of service issue. It could occur if a client sent large option requests, making the server waste CPU time on reading up to 4GB per request. A client could use this flaw to keep the NBD server from serving other requests, resulting in DoS.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2017-15119 affects the Network Block Device server implementation within Quick Emulator version 2.10 and earlier. This issue resides in the NBD server component that handles remote block device access, which is commonly used in virtualization environments to provide network-based storage capabilities. The vulnerability stems from insufficient input validation and resource management within the server's option request processing mechanism. When a malicious client sends a specially crafted option request with an oversized payload, the server allocates excessive computational resources to process these requests. The flaw specifically manifests when the server attempts to read up to 4 gigabytes of data per individual request, consuming significant CPU cycles and memory resources that could otherwise be utilized for legitimate operations.
The technical implementation of this vulnerability can be classified under CWE-400, which addresses Uncontrolled Resource Consumption, and specifically relates to CWE-770, Allocation of Resources Without Limits or Throttling. The NBD server in QEMU processes option requests through a parsing mechanism that does not adequately validate the size of incoming data before attempting to read it into memory. This allows an attacker to craft malicious requests that trigger excessive resource consumption patterns. The server's processing loop continues to consume CPU time and memory resources proportional to the size of the option requests, creating a scenario where legitimate service requests cannot be processed due to resource exhaustion. The vulnerability operates at the protocol level within the NBD implementation, where the server fails to enforce reasonable limits on the size of option data that can be transmitted during the negotiation phase of the NBD protocol.
From an operational perspective, this vulnerability presents a significant denial of service risk to systems running affected QEMU versions. The impact extends beyond simple service disruption as it affects the availability of virtualized environments that rely on NBD for storage operations. Attackers can exploit this flaw by establishing connections to the NBD server and sending large option requests that consume substantial computational resources, effectively starving the server of processing power needed to handle legitimate client requests. The vulnerability is particularly concerning in cloud computing and virtualization environments where multiple tenants share the same infrastructure, as a single malicious client could potentially disrupt services for other users. The resource consumption pattern makes this attack relatively easy to execute and difficult to detect, as it does not require sophisticated techniques beyond crafting oversized network packets.
The remediation for CVE-2017-15119 involves upgrading to QEMU version 2.11 or later, where the NBD server implementation has been patched to properly validate and limit the size of option requests. The fix typically involves implementing size checks on incoming option data before processing, establishing reasonable upper bounds on the amount of data that can be read per request, and implementing timeouts to prevent indefinite processing of large option payloads. Organizations should also implement network-level monitoring to detect unusual patterns of option request processing that could indicate exploitation attempts. Additionally, administrators should consider implementing access controls and rate limiting mechanisms at the network level to restrict the ability of individual clients to consume excessive resources. The mitigation strategy aligns with ATT&CK technique T1499.004, which addresses Network Denial of Service, and emphasizes the importance of resource management and input validation as core security controls. Security teams should also review their virtualization infrastructure configurations to ensure that NBD services are properly isolated and that appropriate resource quotas are enforced to prevent similar vulnerabilities from impacting other services.