CVE-2023-27496 Explained : Impact and Mitigation

This CVE-2023-27496 relates to a vulnerability in Envoy where the application may crash when a redirect URL without a state parameter is received in the OAuth filter.

Understanding CVE-2023-27496

This section will provide insights into the nature, impact, technical details, and mitigation strategies related to CVE-2023-27496.

What is CVE-2023-27496?

CVE-2023-27496 involves an issue in Envoy, an open-source edge and service proxy designed for cloud-native applications. Prior to specific versions, the OAuth filter in Envoy does not properly validate input, assuming the presence of a

state

query parameter in OAuth redirect responses. If a request without the

state

parameter is sent to Envoy's OAuth filter, it can cause the Envoy process to crash.

The Impact of CVE-2023-27496

The impact of this vulnerability is rated as medium severity. An attacker could potentially exploit this issue to disrupt the availability of the Envoy application, leading to service downtime or unavailability.

Technical Details of CVE-2023-27496

In this section, the technical aspects of the CVE-2023-27496 vulnerability are discussed in detail.

Vulnerability Description

The vulnerability arises due to improper input validation in the OAuth filter of Envoy. Versions prior to 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9 are affected, where the absence of a

state

parameter in a redirect URL causes the Envoy process to terminate abnormally.

Affected Systems and Versions

Versions of Envoy affected by this vulnerability include:

Versions greater than or equal to 1.25.0 and less than 1.25.3
Versions greater than or equal to 1.24.0 and less than 1.24.4
Versions greater than or equal to 1.23.0 and less than 1.23.6
Versions earlier than 1.22.9

Exploitation Mechanism

By sending a request to the OAuth filter without the required

state

parameter, an attacker can trigger a crash in the Envoy process, exploiting the absence of proper input validation.

Mitigation and Prevention

This section outlines steps to mitigate the vulnerability and prevent potential exploitation.

Immediate Steps to Take

To address CVE-2023-27496, immediate actions can include:

Updating Envoy to versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, or 1.22.9 that contain the necessary patches.
Implementing strict OAuth traffic controls.
Disabling the OAuth filter if not required.
Filtering incoming traffic before reaching the OAuth filter using measures like Lua scripts.

Long-Term Security Practices

In the long term, it is advisable to:

Regularly update and patch software to ensure the latest security fixes.
Conduct security assessments and audits to identify and address vulnerabilities proactively.
Stay informed about security advisories and best practices in application security.

Patching and Updates

Users and organizations using affected versions of Envoy should prioritize applying the available patches to secure their environments against potential exploitation of CVE-2023-27496.