CVE-2019-15718
Description
An improper authorization flaw was discovered in systemd-resolved in the way it configures the exposed DBus interface org.freedesktop.resolve1. An unprivileged local attacker could call all DBus methods, even when marked as privileged operations. An attacker could abuse this flaw by changing the DNS, Search Domain, LLMNR, DNSSEC and other network link settings without any authorization, allowing control of the network names resolution process and cause the system to communicate with wrong or malicious servers.
Statement
This issue does not affect the versions of systemd as shipped with Red Hat Enterprise Linux 7 as the shipped systemd-resolved does not provide any privileged DBus method. This issue does affect the versions of systemd as shipped with Red Hat Enterprise Linux 8, however the systemd-resolved service is not enabled by default, so the flaw cannot be exploited unless the service was manually enabled.
The flaw was rated as Moderate as it requires a local attacker and changing the DNS servers cannot compromise the system by itself, though it could be used for phishing attacks or to redirect the users to malicious websites. Moreover, on Red Hat Enterprise Linux 8 systemd-resolved needs to be manually enabled by an administrator to make the system vulnerable.
OpenShift Container Platform 4 includes a vulnerable version of systemd on RHEL CoreOS nodes. However, the systemd-resolved service is removed from RHEL CoreOS instances, making this vulnerability not exploitable. This flaw is rated Low for OpenShift Container Platform 4.
Mitigation
Disable systemd-resolved service by using `sudo systemctl disable systemd-resolved`.
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 | 5.3 | 4.4 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | Low | Low | N/A |
| Integrity Impact | Low | Low | N/A |
| Availability Impact | Low | None | N/A |
Vector
Red Hat: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data; Read Files or Directories
An attacker could read sensitive data, either by reading the data directly from a data store that is not properly restricted, or by accessing insufficiently-protected, privileged functionality to read the data.
Integrity
Technical Impact: Modify Application Data; Modify Files or Directories
An attacker could modify sensitive data, either by writing the data directly to a data store that is not properly restricted, or by accessing insufficiently-protected, privileged functionality to write the data.
Access Control
Technical Impact: Gain Privileges or Assume Identity; Execute Unauthorized Code or Commands
When access control checks are not applied consistently - or not at all - an attacker could gain privileges and execute unauthorized code or commands by modifying or reading critical data directly, or by accessing insufficiently-protected, privileged functionality.
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