CVE-2019-19270 : What You Need to Know

ProFTPD through version 1.3.6b is affected by a vulnerability in the tls_verify_crl function. This flaw allows revoked client certificates to establish connections with the server.

Understanding CVE-2019-19270

A vulnerability in ProFTPD's tls_verify_crl function allows certain valid Certificate Revocation Lists (CRLs) to be improperly considered, potentially enabling revoked client certificates to connect to the server.

What is CVE-2019-19270?

This CVE identifies an issue in ProFTPD versions up to 1.3.6b, where the tls_verify_crl function fails to verify the correct field of a Certificate Revocation List (CRL) entry, potentially allowing revoked client certificates to establish connections with the server.

The Impact of CVE-2019-19270

The vulnerability in ProFTPD could lead to revoked client certificates being able to connect to the server, compromising the security and integrity of the system.

Technical Details of CVE-2019-19270

ProFTPD through version 1.3.6b is affected by a vulnerability in the tls_verify_crl function.

Vulnerability Description

The issue arises from the function's failure to properly verify the correct field of a CRL entry, allowing certain valid CRLs to be disregarded and potentially enabling revoked client certificates to establish connections with the server.

Affected Systems and Versions

Product: ProFTPD
Vendor: N/A
Versions affected: Up to 1.3.6b

Exploitation Mechanism

The vulnerability occurs due to the function's incorrect verification process, which only checks the subject field twice instead of both the subject and issuer fields, potentially allowing revoked client certificates to bypass proper validation.

Mitigation and Prevention

Immediate Steps to Take:

Update ProFTPD to a patched version that addresses the vulnerability.
Monitor for any unauthorized connections or unusual activities on the server. Long-Term Security Practices:
Regularly update and patch software to prevent known vulnerabilities.
Implement proper certificate management practices to revoke and manage certificates securely.
Conduct regular security assessments and audits to identify and address potential security risks.
Educate users on secure practices and the importance of certificate validation.

Patching and Updates

Ensure that ProFTPD is updated to version 1.3.6c or later to mitigate the vulnerability and prevent unauthorized connections from revoked client certificates.