CVE-2021-23840 : What You Need to Know

This article discusses CVE-2021-23840, an integer overflow vulnerability in OpenSSL that could lead to applications behaving incorrectly or crashing.

Understanding CVE-2021-23840

In this section, we delve into the details of CVE-2021-23840 to understand its impact and implications.

What is CVE-2021-23840?

CVE-2021-23840 is an integer overflow vulnerability in OpenSSL that affects versions 1.1.1i and below. Calls to specific functions in OpenSSL may cause the output length argument to overflow, potentially leading to application malfunctions or crashes.

The Impact of CVE-2021-23840

The vulnerability could result in applications misbehaving or crashing due to incorrect output length values. OpenSSL versions 1.1.1i and below are affected by this issue.

Technical Details of CVE-2021-23840

This section outlines the technical aspects of CVE-2021-23840.

Vulnerability Description

Calls to EVP_CipherUpdate, EVP_EncryptUpdate, and EVP_DecryptUpdate functions in OpenSSL can lead to output length overflow, causing applications to malfunction or crash.

Affected Systems and Versions

OpenSSL versions 1.1.1i and below are vulnerable. Users of these versions are advised to upgrade to OpenSSL 1.1.1j. OpenSSL 1.0.2x and below are also affected, but OpenSSL 1.0.2 is no longer receiving public updates.

Exploitation Mechanism

In cases where the input length is close to the maximum allowable length for an integer, calls to the vulnerable functions may return success (1) but provide a negative output length value, leading to potential crashes.

Mitigation and Prevention

In this section, we explore the steps to mitigate the risks associated with CVE-2021-23840.

Immediate Steps to Take

Users of affected OpenSSL versions should upgrade to OpenSSL 1.1.1j. Premium support customers using OpenSSL 1.0.2 should upgrade to 1.0.2y to address the vulnerability.

Long-Term Security Practices

Regularly updating OpenSSL to the latest supported versions can help prevent vulnerabilities like CVE-2021-23840 and ensure a secure environment.

Patching and Updates

It is crucial for users to stay informed about security advisories from OpenSSL and apply patches promptly to keep their systems protected.