CVE-2021-21290 : What You Need to Know

Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high-performance protocol servers & clients. In Netty before version 4.1.59.Final, a vulnerability exists on Unix-like systems involving insecure temporary files. This can lead to local information disclosure when temporary storing uploads on disk is enabled. The vulnerability allows for information disclosure in the local system temporary directory that is shared between all users on Unix-like systems. The issue has been fixed in version 4.1.59.Final.

Understanding CVE-2021-21290

Netty, a popular open-source network application framework, faced a security vulnerability related to temporary files on Unix-like systems.

What is CVE-2021-21290?

The vulnerability in Netty version < 4.1.59.Final can result in local information disclosure on Unix-like systems due to insecure temporary files.

The Impact of CVE-2021-21290

The vulnerability allows for local information disclosure via the local system temporary directory on Unix-like systems, potentially exposing sensitive data.

Technical Details of CVE-2021-21290

The vulnerability involves insecure file creation-related permissions, leading to potential information disclosure.

Vulnerability Description

The issue in Netty version < 4.1.59.Final enables local information disclosure on Unix-like systems through insecure temporary file handling.

Affected Systems and Versions

Netty versions prior to 4.1.59.Final on Unix-like systems are affected by this vulnerability.

Exploitation Mechanism

By leveraging insecure temporary files, attackers can exploit this vulnerability to access sensitive information on Unix-like systems.

Mitigation and Prevention

To mitigate the risk associated with CVE-2021-21290, immediate actions and long-term security practices are recommended.

Immediate Steps to Take

One workaround is to specify a unique

java.io.tmpdir

or use

DefaultHttpDataFactory.setBaseDir(...)

to ensure directory permissions that restrict access.

Long-Term Security Practices

Regularly updating Netty to version 4.1.59.Final or higher can help prevent the exploitation of this vulnerability.

Patching and Updates

Ensure timely patching of Netty to version 4.1.59.Final or newer to address the security issues associated with CVE-2021-21290.