CVE-2015-3153 in Enterprise Manager
Summary
by MITRE
The default configuration for cURL and libcurl before 7.42.1 sends custom HTTP headers to both the proxy and destination server, which might allow remote proxy servers to obtain sensitive information by reading the header contents.
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Analysis
by VulDB Data Team • 07/04/2022
The vulnerability identified as CVE-2015-3153 represents a critical configuration flaw in cURL and libcurl versions prior to 7.42.1 that exposes sensitive information through improper header handling during proxy communications. This issue stems from the default behavior where custom HTTP headers are transmitted to both proxy servers and destination servers simultaneously, creating an unintended information leakage channel that adversaries can exploit to gain unauthorized access to confidential data.
The technical flaw manifests when cURL applications operate in proxy environments where custom headers are configured for specific purposes such as authentication tokens, session identifiers, or other sensitive metadata. When these headers are sent to both the proxy and the final destination server, proxy servers that are either malicious or compromised can intercept and analyze the header contents to extract valuable information. This behavior violates the principle of least privilege and creates a scenario where information intended for specific endpoints becomes accessible to intermediate proxy infrastructure that should not have such visibility into client communications.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks including session hijacking, credential theft, and privilege escalation. Attackers can leverage this flaw to harvest authentication tokens, API keys, or other sensitive headers that may contain session identifiers or authorization credentials. The vulnerability is particularly concerning in enterprise environments where proxy servers are commonly used for traffic management, monitoring, or security filtering, as these intermediaries become potential attack vectors for information extraction.
This vulnerability aligns with CWE-200, which addresses information exposure, and represents a specific instance of improper information handling in network communication protocols. The issue also maps to ATT&CK technique T1071.004 for application layer protocol: DNS and T1566.001 for credential access through the information disclosure that enables subsequent exploitation. Organizations using affected versions of cURL and libcurl face significant risk when their applications route traffic through proxy servers, particularly in scenarios involving sensitive data transmission or authentication mechanisms.
Mitigation strategies should prioritize immediate patching to cURL and libcurl versions 7.42.1 and later, which address the header transmission behavior. Administrators should also implement network segmentation to limit proxy server access, configure explicit header filtering to prevent sensitive data from being sent to proxies, and monitor proxy server logs for unusual header patterns. Additionally, organizations should conduct security assessments to identify applications using vulnerable versions and implement proper header management policies that separate proxy-specific headers from those intended for destination servers only.