CVE-2017-7440 in Connect
Summary
by MITRE
Kerio Connect 8.0.0 through 9.2.2, and Kerio Connect Client desktop application for Windows and Mac 9.2.0 through 9.2.2, when e-mail preview is enabled, allows remote attackers to conduct clickjacking attacks via a crafted e-mail message.
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Analysis
by VulDB Data Team • 09/23/2020
The vulnerability identified as CVE-2017-7440 affects Kerio Connect email server versions 8.0.0 through 9.2.2 and its associated desktop client applications for Windows and Mac versions 9.2.0 through 9.2.2. This security flaw manifests when the email preview feature is enabled, creating a significant vector for remote attackers to execute clickjacking attacks against unsuspecting users. The vulnerability stems from insufficient security controls within the email client's rendering engine that fails to properly sanitize or isolate potentially malicious content when displaying email previews, particularly in environments where users have enabled automatic preview functionality. The issue represents a critical weakness in the application's user interface security model, as it allows attackers to manipulate the visual presentation of email content to deceive users into performing unintended actions.
Clickjacking attacks exploit the way web browsers render content by overlaying malicious elements on top of legitimate user interface components, tricking users into clicking on what they believe to be benign elements but are actually malicious actions. In the context of Kerio Connect, when email preview is enabled, the application displays email content directly within the email client interface without proper isolation mechanisms. This creates an environment where attackers can craft specially formatted emails that, when previewed, overlay transparent or semi-transparent elements on top of legitimate interface controls, causing users to inadvertently interact with malicious components. The vulnerability specifically targets the email client's preview functionality, which is commonly enabled by default or by users seeking convenience in email management, making it particularly dangerous as it operates within the normal user workflow.
The operational impact of this vulnerability extends beyond simple phishing attempts, as it can enable more sophisticated attack vectors including credential theft, unauthorized transaction execution, and data exfiltration. Attackers can leverage this vulnerability to create fake login prompts, fraudulent payment interfaces, or malicious file download prompts that appear to be legitimate parts of the email client interface. The attack requires minimal user interaction beyond viewing the malicious email, making it particularly effective in corporate environments where users frequently interact with email clients and may not be adequately trained to recognize such sophisticated social engineering attempts. This vulnerability can be particularly devastating in enterprise settings where Kerio Connect serves as a primary email solution, potentially compromising entire email domains and enabling attackers to gain access to sensitive corporate communications and data.
Security mitigations for CVE-2017-7440 should focus on disabling email preview functionality when possible, as this directly eliminates the attack vector. Organizations should implement strict security policies that disable automatic email preview features, particularly in high-security environments. Network administrators should consider implementing email filtering solutions that can detect and block potentially malicious email content before it reaches users. The vulnerability aligns with CWE-1021, which describes improper restriction of operations within a limited context, and maps to ATT&CK technique T1203, which covers Exploitation for Client Execution. Additionally, this vulnerability demonstrates characteristics of CWE-352, Cross-Site Request Forgery, and CWE-611, Improper Restriction of XML External Entity Reference, as it involves the improper handling of external content within the email client interface. Organizations should also consider implementing user awareness training to recognize potential clickjacking attempts and ensure that all systems are updated to versions that have addressed this vulnerability through proper security patches and code modifications.