CVE-2021-43824 : Exploit Details and Defense Strategies
Learn about CVE-2021-43824 affecting Envoy, a cloud-native proxy service. Understand the impact, affected versions, and mitigation steps to secure your systems.
Envoy is an open-source edge and service proxy. In affected versions, a crafted request crashes Envoy when a CONNECT request is sent to the JWT filter configured with a regex match, leading to a denial of service attack vector. Users are advised to upgrade to mitigate this vulnerability.
Understanding CVE-2021-43824
What is CVE-2021-43824?
Envoy, a cloud-native application service proxy, experiences a null pointer dereference vulnerability in specific versions, which can be exploited to launch a denial of service attack.
The Impact of CVE-2021-43824
The vulnerability has a base severity of HIGH with an impact on availability. An attacker can maliciously craft a request, causing Envoy to crash, impacting service availability.
Technical Details of CVE-2021-43824
Vulnerability Description
The vulnerability arises when a CONNECT request is sent to a JWT filter with a regex match, resulting in a denial of service scenario due to a null pointer dereference issue.
Affected Systems and Versions
- Envoy versions >= 1.20.0 and < 1.20.2
- Envoy versions >= 1.19.0 and < 1.19.3
- Envoy versions < 1.18.6
- Envoy versions >= 1.21.0 and < 1.21.1
Exploitation Mechanism
The vulnerability is exploited through sending a crafted CONNECT request to the JWT filter configured with a regex match, triggering the null pointer dereference flaw.
Mitigation and Prevention
Immediate Steps to Take
- Upgrade Envoy to a non-affected version immediately.
- Avoid using regex in the JWT filter.
Long-Term Security Practices
- Regularly monitor for security advisories and updates.
- Implement a robust incident response plan.
Patching and Updates
- Keep Envoy up to date with the latest security patches to prevent exploitation of vulnerabilities.