CVE-2019-14850
Description
A denial of service vulnerability was discovered in nbdkit. An attacker could connect to the nbdkit service and cause it to perform a large amount of work in initializing backend plugins, by simply opening a connection to the service. This vulnerability could cause resource consumption and degradation of service in nbdkit, depending on the plugins configured on the server-side.
Statement
Red Hat Virtualization Host includes nbdkit as a dependency of libguestfs, and uses it in p2v/v2v migrations. libguestfs uses nbdkit with a Unix domain socket only, so this vulnerability is not exposed to untrusted users.
Red Hat Virtualization 4.2 EUS includes a vulnerable version of nbdkit, however it is used only on the Hypervisor with a Unix domain socket, so this vulnerability is not exposed to untrusted users.
Mitigation
This attack is only possible if nbdkit is configured with a plugin that does a lot of work in its initial .open() callback. Some examples that do a lot of work are nbdkit-ssh-plugin and nbdkit-guestfs-plugin. The nbdkit-memory-plugin is an example that does very little work, and thus is not subject to this vulnerability.
Only attackers that can connect to the nbdkit service can exploit this vulnerability. If nbdkit is not exposed over TCP (eg, nbdkit -U), or is bound only to a private network interface, or is protected by firewall rules, the attack surface is correspondingly limited.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.7 | 3.7 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | Low | Low | N/A |
Vector
Red Hat: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Amplification; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
System resources can be quickly consumed leading to poor application performance or system crash. This may affect network performance and could be used to attack other systems and applications relying on network performance.
Acknowledgements
This issue was discovered by Richard W. M. Jones (Red Hat).
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