CVE-2021-29479 : Exploit Details and Defense Strategies

Ratpack is a toolkit for creating web applications. In versions prior to 1.9.0, a user-supplied

X-Forwarded-Host

header can be exploited to perform cache poisoning affecting a Ratpack server. Learn more about the impact, technical details, and mitigation strategies below.

Understanding CVE-2021-29479

This CVE describes a vulnerability in Ratpack versions before 1.9.0 that allows for cached redirect poisoning using the

X-Forwarded-Host

header.

What is CVE-2021-29479?

In versions prior to 1.9.0, the use of a user-supplied

X-Forwarded-Host

header can lead to cache poisoning if the cache key does not include the

X-Forwarded-Host

header as a cache key.

The Impact of CVE-2021-29479

The vulnerability can be exploited to perform redirect cache poisoning, enabling an attacker to redirect cached redirects to their site instead of the intended location. This poses a high integrity impact and a high severity threat.

Technical Details of CVE-2021-29479

Here are the technical details related to this CVE:

Vulnerability Description

Ratpack versions prior to 1.9.0 are susceptible to cache poisoning through the

X-Forwarded-Host

header, impacting the proper redirection of cached requests.

Affected Systems and Versions

The vulnerability affects Ratpack versions lower than 1.9.0.

Exploitation Mechanism

By manipulating the

X-Forwarded-Host

header, malicious actors can poison the cache system, redirecting cached requests to unauthorized sites.

Mitigation and Prevention

To address CVE-2021-29479 and enhance security, consider the following measures:

Immediate Steps to Take

Ensure that

ServerConfigBuilder::publicAddress

is correctly configured in the production environment to prevent cache poisoning attacks.

Long-Term Security Practices

Regularly update to the latest version of Ratpack and monitor security advisories for any upcoming vulnerabilities.

Patching and Updates

It is crucial to apply the patch provided in Ratpack 1.9.0 to mitigate the risk of cached redirect poisoning.