CVE-2014-0138 in cURL
Summary
by MITRE
The default configuration in cURL and libcurl 7.10.6 before 7.36.0 re-uses (1) SCP, (2) SFTP, (3) POP3, (4) POP3S, (5) IMAP, (6) IMAPS, (7) SMTP, (8) SMTPS, (9) LDAP, and (10) LDAPS connections, which might allow context-dependent attackers to connect as other users via a request, a similar issue to CVE-2014-0015.
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Analysis
by VulDB Data Team • 05/10/2026
The vulnerability identified as CVE-2014-0138 represents a critical connection reuse issue affecting cURL and libcurl versions prior to 7.36.0. This flaw specifically impacts several secure communication protocols including SCP, SFTP, POP3, POP3S, IMAP, IMAPS, SMTP, SMTPS, LDAP, and LDAPS. The vulnerability stems from the default configuration behavior where the software reuses existing connections for subsequent requests without proper authentication context validation. This connection reuse mechanism, while designed to improve performance by reducing connection overhead, creates a significant security risk when multiple users or sessions share the same connection pool. The flaw allows context-dependent attackers to potentially impersonate other users by leveraging existing connections that maintain authentication state from previous sessions.
The technical implementation of this vulnerability involves the improper handling of connection persistence across different user contexts. When cURL or libcurl reuses connections, it maintains the authentication credentials and session state from the previous user's interaction. This creates an attack surface where an unauthorized user could potentially exploit an existing connection to make requests on behalf of another authenticated user. The vulnerability is particularly concerning because it affects multiple protocol families that are commonly used for email and directory services, where authentication credentials are frequently exchanged. The issue is classified under CWE-284 Access Control, as it represents a failure in proper access control mechanisms during connection reuse operations. The vulnerability's similarity to CVE-2014-0015 indicates a pattern of connection reuse flaws that affect secure protocol implementations.
The operational impact of CVE-2014-0138 extends beyond simple authentication bypass to encompass potential data exposure and privilege escalation across multiple service types. Attackers could exploit this vulnerability to access email accounts, modify directory entries, or send unauthorized messages through compromised SMTP connections. The risk is particularly elevated in environments where multiple users share the same application or system that utilizes cURL for network communications. Organizations running services that depend on these vulnerable protocols face potential unauthorized access to sensitive information, including personal email communications, directory service data, and potentially system configuration details. The vulnerability affects both client-side applications that use cURL for network operations and server-side implementations that rely on libcurl for handling secure communications. The attack vector requires minimal privileges and can be executed through normal network requests, making it particularly dangerous in shared or multi-tenant environments.
Mitigation strategies for CVE-2014-0138 primarily focus on updating to patched versions of cURL and libcurl where version 7.36.0 or later resolves the connection reuse behavior. Organizations should implement connection isolation policies that prevent different user contexts from sharing the same connection pool when using secure protocols. System administrators should configure applications to disable connection reuse for sensitive protocols or implement proper session management that validates authentication context before reusing connections. The implementation of proper connection pooling with explicit user context separation can prevent this vulnerability from being exploited. Security teams should also consider implementing network monitoring to detect unusual connection patterns that might indicate exploitation attempts. Additional controls include disabling unnecessary protocols, implementing strict access controls, and regularly auditing application configurations to ensure that connection reuse settings are appropriate for the security requirements of each service. The vulnerability highlights the importance of secure coding practices around connection management and authentication context handling in network libraries.