CVE-2019-14287
Description
A flaw was found in the way sudo implemented running commands with arbitrary user ID. If a sudoers entry is written to allow the attacker to run a command as any user except root, this flaw can be used by the attacker to bypass that restriction.
Statement
This flaw only affects specific, non-default configurations of sudo, in which sudoers configuration entry allows a user to run a command as any user except root, for example:
someuser myhost = (ALL, !root) /usr/bin/somecommand
This configuration allows user "someuser" to run somecommand as any other user except root. However, this flaw also allows someuser to run somecommand as root by specifying the target user using the numeric id of -1. Only the specified command can be run, this flaw does NOT allow user to run other commands that those specified in the sudoers configuration.
Any other configurations of sudo (including configurations that allow user to run commands as any user including root and configurations that allow user to run command as a specific other user) are NOT affected by this flaw.
Red Hat Virtualization Hypervisor includes an affected version of sudo, however the default configuration is not vulnerable to this flaw.
Mitigation
This vulnerability only affects configurations of sudo that have a runas user list that includes an exclusion of root. The most simple example is:
someuser ALL=(ALL, !root) /usr/bin/somecommand
The exclusion is specified using an excalamation mark (!). In this example, the "root" user is specified by name. The root user may also be identified in other ways, such as by user id:
someuser ALL=(ALL, !#0) /usr/bin/somecommand
or by reference to a runas alias:
Runas_Alias MYGROUP = root, adminuser
someuser ALL=(ALL, !MYGROUP) /usr/bin/somecommand
To ensure your sudoers configuration is not affected by this vulnerability, we recommend examining each sudoers entry that includes the `!` character in the runas specification, to ensure that the root user is not among the exclusions. These can be found in the /etc/sudoers file or files under /etc/sudoers.d.
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 | 7 | 8.8 | N/A |
| Attack Vector | Local | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | 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:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Access Control
Technical Impact: Gain Privileges or Assume Identity
A user can access restricted functionality and/or sensitive information that may include administrative functionality and user accounts.
Acknowledgements
Red Hat would like to thank the Sudo project for reporting this issue. Upstream acknowledges Joe Vennix (Apple Information Security) as the original reporter.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
