CVE-2020-14312
Description
A flaw was found in the default configuration of dnsmasq, as shipped with Fedora and Red Hat Enterprise Linux, where it listens on any interface and accepts queries from addresses outside of its local subnet. In particular, the option local-service is not enabled. Running dnsmasq in this manner may inadvertently make it an open resolver accessible from any address on the internet. This flaw allows an attacker to conduct a Distributed Denial of Service (DDoS) against other systems.
Statement
Even though Red Hat Enterprise Linux 8 and Fedora do not ship a secure default, they have firewalld service enabled by default, which denies incoming DNS queries, preventing this potential attack vector.
In Red Hat OpenStack Platform 13, the dnsmasq package is pulled directly from the RHEL channel and not the RHOSP channel. RHOSP is therefore unaffected, but please ensure that the underlying Red Hat Enterprise Linux dnsmasq package is current.
Mitigation
To restrict the DNS server to queries coming from the local subnet, add `local-service` to your /etc/dnsmasq.conf file or in a file in /etc/dnsmasq.d. A firewall can be configured for additional protection against undesired traffic.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4 | 5.9 | 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 | Changed | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | Low | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/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:H
Understanding the Weakness (CWE)
Other
Technical Impact: Varies by Context
Acknowledgements
Red Hat would like to thank bdrpc for reporting this issue.
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