CVE-2021-43825 : What You Need to Know

Envoy is an open source edge and service proxy designed for cloud-native applications. A use-after-free vulnerability in Envoy could lead to a denial of service attack due to incorrect handling of buffer overflow during response processing.

Understanding CVE-2021-43825

What is CVE-2021-43825?

Envoy is vulnerable to a use-after-free issue where a buffer overflow during response processing can result in accessing freed memory blocks, leading to a denial of service by crashing the system.

The Impact of CVE-2021-43825

CVSS Base Score: 6.1 (Medium)
Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Changed
Confidentiality Impact: None
Integrity Impact: Low
Availability Impact: Low
The vulnerability allows an attacker to exploit the buffer overflow and crash the system, causing a denial of service.

Technical Details of CVE-2021-43825

Vulnerability Description

Envoy does not correctly handle buffer overflow during response processing, leading to a use-after-free scenario and crash.

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

When the buffer overflows during response processing by the filter chain, an operation accessing freed memory blocks may occur, crashing Envoy and causing a denial of service.

Mitigation and Prevention

Immediate Steps to Take

Update Envoy to versions 1.18.6, 1.19.3, 1.20.2, or 1.21.1 to mitigate the vulnerability.
Monitor for unusual behavior that could indicate an exploitation attempt.

Long-Term Security Practices

Implement secure coding practices to prevent buffer overflow vulnerabilities.
Regularly update and patch software to address known security issues.

Patching and Updates

Apply patches provided by the vendor to fix the use-after-free vulnerability in Envoy.