CVE-2016-10727 in evolution-data-server
Summary
by MITRE
camel/providers/imapx/camel-imapx-server.c in the IMAPx component in GNOME evolution-data-server before 3.21.2 proceeds with cleartext data containing a password if the client wishes to use STARTTLS but the server will not use STARTTLS, which makes it easier for remote attackers to obtain sensitive information by sniffing the network. The server code was intended to report an error and not proceed, but the code was written incorrectly.
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Analysis
by VulDB Data Team • 04/25/2023
The vulnerability identified as CVE-2016-10727 resides within the IMAPx component of GNOME evolution-data-server, specifically in the camel-imapx-server.c file. This flaw represents a critical security issue that undermines the intended cryptographic protection mechanisms of email communication protocols. The vulnerability manifests when a client attempts to establish a secure connection using STARTTLS encryption, but the server fails to properly enforce the encryption requirement. According to CWE-310, this constitutes a weakness in cryptographic key handling where the system does not adequately protect sensitive information during transmission. The flaw allows for cleartext password transmission even when the client explicitly requests secure communication, creating a significant attack surface for man-in-the-middle adversaries who can intercept network traffic using standard packet sniffing tools.
The technical implementation error stems from incorrect code logic within the server-side authentication handling mechanism. When the client initiates a connection and expresses intent to use STARTTLS, the server should enforce mandatory encryption before proceeding with any authentication data exchange. However, the flawed implementation in evolution-data-server versions prior to 3.21.2 fails to properly validate the encryption state and continues processing authentication credentials in cleartext format. This incorrect flow violates fundamental security principles outlined in the NIST SP 800-52 standard for secure network communication, where cryptographic protocols must be properly enforced to prevent downgrade attacks. The vulnerability operates at the application layer and specifically affects the IMAP protocol implementation within the GNOME desktop environment's email handling infrastructure.
The operational impact of this vulnerability is severe and directly enables credential theft for remote attackers who can monitor network traffic. An attacker positioned within the network path between the email client and server can capture the cleartext password transmission, effectively bypassing the intended security controls. This weakness aligns with ATT&CK technique T1046 which describes network service scanning and exploitation of protocol vulnerabilities, and T1566 which covers credential harvesting through network sniffing. The vulnerability is particularly dangerous in environments where email servers are accessed over untrusted networks or wireless connections, as it provides attackers with a straightforward method to obtain valid authentication credentials without requiring additional exploitation techniques. The flaw essentially creates a backdoor for password capture that undermines the entire security model of email authentication systems.
Mitigation strategies for CVE-2016-10727 focus primarily on upgrading to the patched version of GNOME evolution-data-server 3.21.2 or later, which corrects the flawed code logic and properly enforces encryption requirements. Organizations should implement network monitoring to detect and alert on unusual authentication patterns that might indicate exploitation attempts. The fix addresses the root cause by ensuring that when STARTTLS is requested by the client, the server properly validates the encryption state before processing any authentication data, preventing the cleartext transmission of sensitive information. Security administrators should also consider implementing additional network security controls such as encrypted network segmentation and mandatory encryption policies for email protocols. This vulnerability demonstrates the critical importance of proper cryptographic protocol enforcement and the potential for seemingly minor implementation errors to create significant security weaknesses in enterprise email infrastructure.