CVE-2021-22926 Explained : Impact and Mitigation

A vulnerability has been discovered in libcurl-using applications that could allow a malicious user to trick the application to use a wrong client certificate, resulting in sending the wrong certificate in the TLS connection handshake.

Understanding CVE-2021-22926

This CVE affects libcurl-using applications and involves the macOS native TLS library Secure Transport where a malicious user can manipulate the client certificate used in a transfer.

What is CVE-2021-22926?

Applications using libcurl with Secure Transport on macOS can be tricked into using an incorrect client certificate by a malicious user creating a file with the same name as the certificate the application wants to use.

The Impact of CVE-2021-22926

The vulnerability could lead to the improper use of client certificates, potentially compromising the security of TLS connections and sensitive data transmission.

Technical Details of CVE-2021-22926

This section provides an overview of the vulnerability, the affected systems, and the exploitation mechanism.

Vulnerability Description

The flaw in libcurl-using applications allows a malicious user to manipulate the client certificate selection by creating a file with the same name as the intended certificate.

Affected Systems and Versions

The vulnerability impacts libcurl versions 7.33.0 to 7.77.0 when using Secure Transport on macOS.

Exploitation Mechanism

By creating a file with the same name as the client certificate requested by the application in a writable directory, a malicious user can trick the application into using the incorrect certificate.

Mitigation and Prevention

To protect systems from this vulnerability, immediate steps must be taken along with implementing long-term security practices and ensuring timely patching and updates.

Immediate Steps to Take

Ensure that the application's working directory is not writable by unauthorized users to prevent the manipulation of client certificates.

Long-Term Security Practices

Implement secure coding practices, regularly review and update security configurations, and conduct security testing to detect and prevent similar vulnerabilities.

Patching and Updates

Update libcurl to a patched version that addresses the vulnerability and follow best practices for secure client certificate handling to mitigate risks.