CVE-2019-3876
Description
A flaw was found in the /oauth/token/request custom endpoint of the OpenShift OAuth server allowing for XSS generation of CLI tokens due to missing X-Frame-Options and CSRF protections. If not otherwise prevented, a separate XSS vulnerability via JavaScript could further allow for the extraction of these tokens.
Statement
This issue affects the OAuth server shipped in OpenShift Container Platform version v3.0 through v3.11. Red Hat Product Security has rated this issue as having a security impact of Moderate.
For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.
Mitigation
Since at least v3.4, the OpenShift documentation [1] has specified the format for corsAllowedOrigins to accurately match intended hostnames. Since at least v3.7, installs will default to use the correct regular expression formatted variables. Earlier versions may be configured with plain strings, a configuration which will persist across cluster upgrades, opening them to cross origin vulnerabilities such as this.
At a minimum, you should ensure that the corsAllowedOrigin definition within master-config.yaml contains elements in the form
corsAllowedOrigins:
- (?i)//my\.subdomain\.domain\.com(:|\z)
and not the form
corsAllowedOrigins:
- domain.com
as the first will permit cross origin requests only if the host matches exactly, whereas the second will permit from any host that merely contains the string (such as ABCDdomain.com or even domain.comABCD.com).
Footnotes:
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 | 6.3 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | Required | Required | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | Low | Low | N/A |
| Integrity Impact | Low | Low | N/A |
| Availability Impact | Low | Low | N/A |
Vector
Red Hat: CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:L
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability,Non-Repudiation,Access Control
Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism; Read Application Data; Modify Application Data; DoS: Crash, Exit, or Restart
The consequences will vary depending on the nature of the functionality that is vulnerable to CSRF. An attacker could trick a client into making an unintentional request to the web server via a URL, image load, XMLHttpRequest, etc., which would then be treated as an authentic request from the client - effectively performing any operations as the victim, leading to an exposure of data, unintended code execution, etc. If the victim is an administrator or privileged user, the consequences may include obtaining complete control over the web application - deleting or stealing data, uninstalling the product, or using it to launch other attacks against all of the product's users. Because the attacker has the identity of the victim, the scope of CSRF is limited only by the victim's privileges.
Acknowledgements
This issue was discovered by Mo Khan (Red Hat).
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