CVE-2018-16586 in Open Ticket Request System
Summary
by MITRE
In Open Ticket Request System (OTRS) 4.0.x before 4.0.32, 5.0.x before 5.0.30, and 6.0.x before 6.0.11, an attacker could send a malicious email to an OTRS system. If a logged in user opens it, the email could cause the browser to load external image or CSS resources.
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Analysis
by VulDB Data Team • 05/19/2023
The vulnerability identified as CVE-2018-16586 affects the Open Ticket Request System OTRS, a widely used help desk and ticket management platform. This security flaw exists in multiple versions of the software including 4.0.x before 4.0.32, 5.0.x before 5.0.30, and 6.0.x before 6.0.11, representing a significant risk to organizations relying on these systems for their customer service operations. The vulnerability stems from insufficient input validation and sanitization within the email processing functionality of the OTRS platform.
The technical flaw manifests when an attacker crafts a malicious email and delivers it to a targeted OTRS system. When a logged-in user opens this email within the OTRS interface, the system automatically processes and displays the email content. Due to inadequate filtering of external resource references, the malicious email can contain embedded links to external image or CSS resources that are automatically loaded by the user's browser. This occurs because the OTRS system does not properly sanitize or block external resource requests that may be embedded within email content, particularly within HTML formatted messages.
The operational impact of this vulnerability is substantial and aligns with CWE-116, which addresses improper encoding or escaping of output. Attackers can leverage this weakness to perform various malicious activities including tracking user behavior, delivering additional malware payloads, or conducting cross-site scripting attacks. The vulnerability creates a vector for information leakage where an attacker can monitor which users open specific emails, potentially gathering intelligence about user activity patterns and system access. This represents a significant privacy and security concern for organizations handling sensitive customer data through their OTRS implementations.
From an attack framework perspective, this vulnerability maps to the initial access phase of the ATT&CK framework, specifically under the technique of "Phishing" with the sub-technique "Spearphishing Attachment." The attack chain begins with the delivery of a malicious email, followed by user interaction that triggers the execution of external resource requests. Organizations using OTRS are particularly vulnerable because the system automatically processes and displays external resources without proper security controls, making it an attractive target for attackers seeking to exploit user trust and system integration.
The primary mitigation strategy involves upgrading to patched versions of OTRS where the vulnerability has been addressed through improved input validation and resource filtering mechanisms. Organizations should also implement email filtering solutions that can identify and block potentially malicious content before it reaches users, and consider configuring network-level restrictions to prevent access to external resources from within the OTRS environment. Additionally, user education regarding the risks of opening suspicious emails and implementing proper security policies for email handling can significantly reduce the attack surface. Network segmentation and monitoring solutions should be deployed to detect anomalous external resource requests that may indicate exploitation attempts. The vulnerability demonstrates the importance of maintaining current security patches and implementing defense-in-depth strategies to protect against email-based attack vectors that leverage browser-based resource loading mechanisms.