CVE-2021-43826 Explained : Impact and Mitigation
Learn about CVE-2021-43826, a high-impact vulnerability in Envoy affecting specific versions. Discover the impact, affected systems, and mitigation steps for this security issue.
Envoy is an open-source edge and service proxy that encountered a crash issue when configured for upstream tunneling and the downstream connection disconnects. This vulnerability affects specific versions of Envoy.
Understanding CVE-2021-43826
In this section, we will delve into the details of the Envoy vulnerability identified as CVE-2021-43826.
What is CVE-2021-43826?
CVE-2021-43826 refers to a vulnerability in Envoy that leads to a crash scenario when configured for upstream tunneling, and the downstream connection disconnects prematurely.
The Impact of CVE-2021-43826
The impact of this CVE includes:
- CVSS Score: 7.5 (High)
- Attack Vector: Network
- Availability Impact: High
- Type: Use After Free (CWE-416)
This vulnerability poses a high-risk scenario where an attacker can exploit the crash to impact the availability of the affected systems.
Technical Details of CVE-2021-43826
Let's explore the technical aspects associated with CVE-2021-43826.
Vulnerability Description
In affected versions of Envoy, a crash occurs during upstream tunneling when the downstream connection disconnects prematurely while the upstream connection or HTTP/2 stream is still being established.
Affected Systems and Versions
The following versions of Envoy are affected:
- Envoy < 1.18.6
- Envoy >= 1.19.0, < 1.19.3
- Envoy >= 1.20.0, < 1.20.2
- Envoy >= 1.21.0, < 1.21.1
Exploitation Mechanism
The vulnerability can be exploited when configuring Envoy for upstream tunneling and inducing premature disconnection of downstream connections.
Mitigation and Prevention
To address CVE-2021-43826, the following steps are recommended:
Immediate Steps to Take
- Upgrade affected Envoy instances to versions that are not vulnerable.
Long-Term Security Practices
- Regularly monitor and apply security patches to Envoy.
- Implement network segmentation to contain potential attacks.
Patching and Updates
Ensure timely application of security patches and updates provided by Envoy to mitigate the vulnerability.