CVE-2003-1605 in cURL
Summary
by MITRE
curl 7.x before 7.10.7 sends CONNECT proxy credentials to the remote server.
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Analysis
by VulDB Data Team • 03/17/2020
The vulnerability identified as CVE-2003-1605 affects curl versions prior to 7.10.7 and represents a critical security flaw in proxy authentication handling. This issue stems from improper credential management during proxy connections where the client application fails to properly isolate proxy authentication credentials from the actual remote server authentication context. The flaw manifests when curl establishes a connection through a proxy server using the CONNECT method, which is commonly employed for https tunneling and other secure communications. During this process, the vulnerable version of curl inadvertently forwards proxy authentication credentials to the ultimate remote server, creating an unexpected and potentially dangerous credential exposure scenario.
This technical vulnerability can be classified under CWE-287 which specifically addresses improper authentication mechanisms, and more broadly under CWE-306 which deals with missing authentication. The flaw operates at the application layer of the network stack where curl processes proxy requests and authentication. When a user configures curl to connect through a proxy server with authentication credentials, the software incorrectly propagates these credentials beyond the proxy boundary to the target server. This behavior violates fundamental security principles of credential isolation and access control, as proxy credentials should remain confined to the proxy server context and not be transmitted to downstream services.
The operational impact of this vulnerability extends beyond simple credential leakage to potentially enable unauthorized access to remote services. An attacker who gains control of a proxy server or can intercept proxy communications can exploit this flaw to obtain valid authentication credentials that may grant access to protected resources behind the proxy. The vulnerability particularly affects environments where multiple authentication layers exist and where proxy servers are used for network access control. Organizations using older curl versions in their infrastructure face significant risk, especially in enterprise environments where proxy authentication is commonly implemented for security and compliance purposes. The flaw can be exploited through various attack vectors including man-in-the-middle scenarios where attackers can manipulate proxy communication flows to capture and reuse credentials.
Mitigation strategies for CVE-2003-1605 require immediate software updates to curl version 7.10.7 or later, which properly implements credential isolation during proxy connections. Security administrators should conduct comprehensive inventory audits to identify all systems running vulnerable curl versions and prioritize patching efforts accordingly. Network segmentation and monitoring solutions should be implemented to detect unusual credential transmission patterns that might indicate exploitation attempts. Organizations should also review their proxy server configurations and authentication policies to minimize the impact of potential credential exposure. The ATT&CK framework categorizes this vulnerability under T1566 which covers credential harvesting through social engineering and T1071 which deals with application layer protocol usage, highlighting the need for both defensive and detection measures. Additional controls such as network access controls, secure credential storage mechanisms, and regular security assessments can help reduce the risk associated with this vulnerability while the primary patch is being deployed across affected systems.