CVE-2007-5034 in ELinks
Summary
by MITRE
ELinks before 0.11.3, when sending a POST request for an https URL, appends the body and content headers of the POST request to the CONNECT request in cleartext, which allows remote attackers to sniff sensitive data that would have been protected by TLS. NOTE: this issue only occurs when a proxy is defined for https.
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Analysis
by VulDB Data Team • 06/04/2025
The vulnerability described in CVE-2007-5034 represents a critical flaw in the ELinks web browser's handling of HTTPS proxy connections, specifically affecting versions prior to 0.11.3. This issue demonstrates a fundamental misunderstanding of how TLS encryption should be applied in proxy environments, creating a scenario where sensitive data that should remain protected within the encrypted tunnel becomes exposed to network sniffing attacks.
The technical flaw occurs when ELinks attempts to establish a secure connection through an HTTPS proxy server. During this process, the browser creates a CONNECT request to the proxy server to initiate the tunnel. However, instead of properly isolating the TLS encryption boundaries, the software incorrectly appends the POST request body and associated content headers to this CONNECT request in cleartext format. This misconfiguration effectively breaks the TLS encryption layer by exposing sensitive information that should have been protected within the secure tunnel between the client and the target server.
This vulnerability operates under the principle of improper handling of secure communication protocols and falls under the category of weak cryptographic practices as defined by CWE-310. The flaw specifically manifests when a proxy server is configured for HTTPS connections, making it a proxy-related security issue that violates the fundamental expectations of how HTTPS tunneling should function. The attack vector involves network sniffing, where remote attackers can capture and analyze the cleartext portions of what should have been encrypted traffic.
The operational impact of this vulnerability is significant as it compromises the confidentiality of data transmitted through HTTPS proxy connections. Any sensitive information including authentication credentials, personal data, or business-critical information that is sent via POST requests through an HTTPS proxy becomes vulnerable to interception. This issue particularly affects organizations that rely on proxy infrastructure for web access control and security monitoring, as it undermines the security assurances provided by TLS encryption. The vulnerability is classified under the attack technique of credential access and data exfiltration as outlined in the MITRE ATT&CK framework, specifically targeting the compromise of encrypted communications.
Mitigation strategies for this vulnerability require immediate patching of ELinks to version 0.11.3 or later, which addresses the improper handling of proxy CONNECT requests. Organizations should also consider implementing network monitoring to detect unusual traffic patterns that might indicate exploitation attempts. Additionally, security teams should review their proxy configurations and ensure that proper TLS handling is enforced at all levels of the network infrastructure. The fix implemented in the patched version ensures that POST request bodies and headers are properly separated from the CONNECT request, maintaining the integrity of the TLS encryption boundaries and preventing the leakage of sensitive data through cleartext transmission.