CVE-2019-14851 in nbdkit
Summary
by MITRE • 03/19/2021
A denial of service vulnerability was discovered in nbdkit. A client issuing a certain sequence of commands could possibly trigger an assertion failure, causing nbdkit to exit. This issue only affected nbdkit versions 1.12.7, 1.14.1, and 1.15.1.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 04/02/2021
The vulnerability identified as CVE-2019-14851 represents a critical denial of service weakness in the nbdkit network block device server software. This flaw manifests when a malicious client crafts and submits a specific sequence of commands to the nbdkit service, triggering an assertion failure that results in the complete termination of the service. The vulnerability specifically impacts versions 1.12.7, 1.14.1, and 1.15.1 of nbdkit, creating a targeted attack surface where legitimate users could be disrupted by carefully constructed command sequences. The issue stems from inadequate input validation and error handling within the command processing pipeline of the network block device server, which fails to properly sanitize or reject malformed command sequences that could cause the software to crash.
The technical execution of this vulnerability involves the exploitation of a flaw in the protocol handling layer of nbdkit where assertion checks are performed on client-provided data without sufficient validation. When a client sends commands that trigger these assertions, the software's defensive mechanisms cause it to terminate abruptly rather than gracefully handling the malformed input. This behavior aligns with CWE-691, which describes insufficient control flow management in software systems, particularly when dealing with externally provided inputs that should be treated as untrusted. The assertion failure mechanism essentially provides an attack vector where an adversary can cause a service disruption by sending carefully crafted command sequences that bypass normal error handling procedures and directly trigger the assertion points within the software's codebase.
From an operational perspective, this vulnerability creates significant risk for systems that rely on nbdkit for virtualization and storage services, particularly in cloud environments and virtual machine management platforms where network block device functionality is essential. The impact extends beyond simple service disruption to potentially affect availability of virtualized storage resources, as the service termination could cause cascading failures in dependent systems. Organizations using affected versions of nbdkit face the risk of unauthorized users causing deliberate service outages that could impact production environments, backup systems, or disaster recovery mechanisms that depend on network block device functionality. The vulnerability's exploitation requires minimal technical expertise, making it accessible to attackers who wish to disrupt services without requiring advanced penetration testing skills.
The mitigation strategy for CVE-2019-14851 primarily involves upgrading to a patched version of nbdkit where the command validation and assertion handling has been improved to properly reject or gracefully handle malformed command sequences. System administrators should prioritize patching affected installations, particularly in environments where nbdkit serves critical storage functions. Additionally, implementing network-level controls such as firewalls or access control lists can help limit exposure by restricting client access to nbdkit services. The vulnerability demonstrates the importance of proper input validation and error handling in network services, aligning with ATT&CK technique T1499.004 for network denial of service attacks. Organizations should also consider implementing monitoring and alerting for unexpected nbdkit service terminations, as this could serve as an indicator of exploitation attempts. The incident highlights the need for comprehensive security testing of protocol implementations and the importance of maintaining up-to-date software versions to protect against known vulnerabilities.