CVE-2021-39155 : What You Need to Know
Learn about CVE-2021-39155 affecting Istio versions, allowing attackers to bypass authorization policies. Explore impacts, mitigation steps, and long-term security practices.
Istio is an open-source platform for integrating microservices with features like traffic management and policy enforcement. A vulnerability allowed bypassing authorization policies due to case sensitivity in host comparison.
Understanding CVE-2021-39155
This CVE pertains to a vulnerability in Istio versions <= 1.9.8, >= 1.10.0, < 1.10.4, and >= 1.11.0, < 1.11.1 related to case sensitivity in host header comparison.
What is CVE-2021-39155?
A flaw in Istio's authorization policy module led to case-sensitive comparisons in the HTTP Host header, enabling attackers to bypass policies by manipulating hostname cases.
The Impact of CVE-2021-39155
The vulnerability scored a CVSS base score of 8.3 (High severity) due to its potential for high confidentiality and integrity impacts without requiring special privileges.
Technical Details of CVE-2021-39155
The technical aspects of this CVE provide insights into the vulnerability's description, affected systems, and how exploitation occurred.
Vulnerability Description
The vulnerability allowed bypassing authorization policies in Istio due to the case sensitivity of HTTP Host header comparisons.
Affected Systems and Versions
- Versions affected: <= 1.9.8, >= 1.10.0, < 1.10.4, and >= 1.11.0, < 1.11.1
Exploitation Mechanism
Attackers exploited the case sensitivity flaw in host header comparisons to manipulate hostnames and bypass Istio authorization policies.
Mitigation and Prevention
Understanding mitigation steps and preventative measures is crucial in addressing CVE-2021-39155.
Immediate Steps to Take
- Apply patches available in Istio 1.11.1, 1.10.4, and 1.9.8 to mitigate the vulnerability effectively.
- Consider implementing Lua filters to normalize Host headers before authorization checks, as outlined in Istio's Security Best Practices.
Long-Term Security Practices
- Regularly update Istio to the latest secure versions to prevent future vulnerabilities.
Patching and Updates
- Stay informed about security advisories and promptly apply patches to secure Istio deployments.