CVE-2021-21374 : Exploit Details and Defense Strategies

Nimble is a package manager for the Nim programming language. In Nim release versions before versions 1.2.10 and 1.4.4, "nimble refresh" fetches a list of Nimble packages over HTTPS without full verification of the SSL/TLS certificate due to the default setting of httpClient. An attacker able to perform MitM can deliver a modified package list containing malicious software packages. If the packages are installed and used, the attack escalates to untrusted code execution.

Understanding CVE-2021-21374

This CVE relates to a vulnerability in Nimble, the package manager for the Nim programming language, that fails to validate SSL/TLS certificates due to insecure default settings in httpClient.

What is CVE-2021-21374?

Nimble, in versions prior to 1.2.10 and 1.4.4, does not perform full verification of SSL/TLS certificates when fetching package lists over HTTPS, making it susceptible to Man-in-the-Middle (MitM) attacks.

The Impact of CVE-2021-21374

The vulnerability poses a high severity risk, with the potential for an attacker to deliver a list of modified packages containing malicious software. If these packages are installed, it can lead to untrusted code execution.

Technical Details of CVE-2021-21374

This section outlines the technical details of the CVE including the vulnerability description, affected systems, and the exploitation mechanism.

Vulnerability Description

The insecure default settings in Nimble allow an attacker to deliver altered packages over HTTPS, leading to the execution of untrusted code on vulnerable systems.

Affected Systems and Versions

Nimble versions prior to 1.2.10 and 1.4.4 are impacted by this vulnerability due to the lack of SSL/TLS certificate validation during package list retrieval.

Exploitation Mechanism

An attacker capable of conducting a Man-in-the-Middle attack can exploit this vulnerability by providing a tampered package list during installation, resulting in the execution of malicious code.

Mitigation and Prevention

To address CVE-2021-21374, immediate steps should be taken to secure systems and prevent potential exploitation.

Immediate Steps to Take

Users are advised to update Nimble to versions 1.2.10 or 1.4.4 to mitigate the vulnerability. Additionally, implementing secure network configurations can help prevent MitM attacks.

Long-Term Security Practices

Establishing a robust software development lifecycle, conducting regular security audits, and ensuring secure coding practices can enhance overall system security.

Patching and Updates

Regularly monitoring for security advisories from vendors like nim-lang and applying patches promptly can safeguard against known vulnerabilities.