CVE-2023-27535: Medium severity IBM IBM® Engineering Requirements Management DOORS vulnerability

An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials being used during subsequent transfers. Previously created connections are kept in a connection pool for reuse if they match the current setup. However, certain FTP settings such as CURLOPTFTPACCOUNT, CURLOPTFTPALTERNATIVETOUSER, CURLOPTFTPSSLCCC, and CURLOPTUSESSL were not included in the configuration match checks, causing them to match too easily. This could lead to libcurl using the wrong credentials when performing a transfer, potentially allowing unauthorized access to sensitive information.

cURL libcurl could allow a remote attacker to bypass security restrictions, caused by a FTP too eager connection reuse flaw. By sending a specially crafted request, an attacker could exploit this vulnerability to reuse a previously created FTP connection.

— IBM

libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them matches the setup. However, several FTP settings were left out from the configuration match checks, making them match too easily. The settings in questions are CURLOPTFTPACCOUNT, CURLOPTFTPALTERNATIVETOUSER, CURLOPTFTPSSLCCC and CURLOPTUSESSL level.

— Red Hat