CVE-2020-6581
Description
A flaw was found in nrpe. A command injection is possible due to insufficient filtering. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
Statement
Nagios is considered deprecated. Nagios plugins and Nagios server are no longer maintained or supported. Refer following release notes for details: "https://access.redhat.com/documentation/en-us/red_hat_gluster_storage/3.5/html-single/3.5_release_notes/index". The older version of nrpe which was shipped with Red Hat Gluster Storage does not support v3 packet format.
Mitigation
Disable nasty_metachars and dont_blame_nrpe option inside the NRPE configuration file - /etc/nagios/nrpe.cfg
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 | 7.3 | 7.3 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | Required | Required | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
To exploit this vulnerability(perform command line injection) an attacker need to access the target system locally (e.g., keyboard, console), or remotely (e.g., SSH). Hence, changing Attack Vector (AV) from Network (N) to Local (L).
Here, attacker would be an authenticated local user, since user level access required to gain local access. Hence, Privileges required (PR) is set to Low.
Victim/user must have compiled NRPE with command line parameter support. Additionally, dont_blame_nrpe option inside the NRPE configuration file has to be enabled. Meeting these both requirements, this vulnerability can be exploited by accepting additional parameters that are passed as command line parameters to the configured monitoring scripts. Hence, User Interaction is set to Required(UI:R).
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If a malicious user injects a character (such as a semi-colon) that delimits the end of one command and the beginning of another, it may be possible to then insert an entirely new and unrelated command that was not intended to be executed. This gives an attacker a privilege or capability that they would not otherwise have.
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