CVE-2021-29495 : What You Need to Know

Nim is a statically typed compiled systems programming language. In Nim standard library before 1.4.2, httpClient SSL/TLS certificate verification was disabled by default. Users can upgrade to version 1.4.2 to receive a patch or, as a workaround, set "verifyMode = CVerifyPeer" as documented.

Understanding CVE-2021-29495

In this CVE, Nim stdlib httpClient does not validate peer certificates by default.

What is CVE-2021-29495?

Nim standard library before version 1.4.2 had an issue where httpClient SSL/TLS certificate verification was not mandatory, exposing users to potential risks if certificates were not validated.

The Impact of CVE-2021-29495

The impact of this vulnerability is rated as MEDIUM based on the CVSSv3.1 scoring. It has a base score of 5.9, with high integrity impact but no impact on confidentiality and availability.

Technical Details of CVE-2021-29495

Vulnerability Description

The vulnerability arises from the lack of default SSL/TLS certificate verification in the Nim stdlib httpClient, allowing potential attackers to exploit this weakness.

Affected Systems and Versions

Systems using Nim standard library versions earlier than 1.4.2 are affected by this vulnerability.

Exploitation Mechanism

Attackers can exploit this vulnerability by performing man-in-the-middle attacks to intercept communication between the httpClient and a server.

Mitigation and Prevention

To address CVE-2021-29495:

Immediate Steps to Take

Users should upgrade to Nim version 1.4.2 or later to receive the necessary patch. Alternatively, setting "verifyMode = CVerifyPeer" can provide a temporary workaround.

Long-Term Security Practices

Developers should implement proper SSL/TLS certificate validation in their applications to prevent similar vulnerabilities.

Patching and Updates

Regularly update Nim and associated libraries to ensure the latest security patches are applied.