CVE-2016-9107 in Gajim
Summary
by MITRE
The OTR plugin for Gajim sends information in cleartext when using XHTML, which allows remote attackers to obtain sensitive information via unspecified vectors.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2016-9107 affects the Off-the-Record Messaging plugin within the Gajim instant messaging client, representing a critical security flaw in end-to-end encrypted communication protocols. This issue specifically manifests when the OTR plugin utilizes XHTML formatting for message transmission, creating an unintended cleartext exposure that compromises the confidentiality assurances typically provided by the encryption mechanism. The vulnerability stems from the improper handling of sensitive data within the XHTML message structure, where information that should remain encrypted is transmitted in plaintext format, thereby undermining the core security objectives of the OTR protocol.
Technical exploitation of this vulnerability occurs through the manipulation of message formatting parameters within the Gajim client's OTR plugin implementation. When XHTML is enabled for message display, the plugin fails to properly encrypt all message components, leaving certain metadata or content elements vulnerable to interception. The flaw operates at the application layer and can be leveraged by remote attackers to capture sensitive information including but not limited to message content, user presence data, and potentially authentication tokens or session identifiers. This represents a direct violation of the fundamental security principles governing encrypted messaging systems, where the integrity and confidentiality of communications must be maintained throughout the entire transmission lifecycle.
The operational impact of CVE-2016-9107 extends beyond simple information disclosure, as it fundamentally compromises the trust model that users place in encrypted messaging applications. Attackers can exploit this vulnerability to perform passive reconnaissance and active data interception, potentially gaining access to private conversations, user credentials, and other sensitive information that would normally be protected by the OTR encryption framework. The vulnerability affects users who rely on Gajim for secure communications, particularly in environments where network traffic monitoring is prevalent, as the cleartext transmission creates observable patterns that can be exploited for targeted attacks. This weakness particularly impacts organizations and individuals who depend on secure communication channels for sensitive discussions, making it a significant concern for privacy-conscious users and enterprises alike.
Mitigation strategies for this vulnerability should prioritize immediate plugin updates and configuration adjustments within the Gajim client environment. Security administrators should disable XHTML message formatting when using OTR encryption to prevent cleartext exposure, while also implementing network monitoring to detect unusual traffic patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-312 (Cleartext Storage of Sensitive Information) and CWE-319 (Cleartext Transmission of Sensitive Information) categories, representing a clear violation of secure coding practices that mandate encryption of all sensitive data regardless of transmission format. From an ATT&CK framework perspective, this vulnerability maps to T1041 (Exfiltration Over C2 Channel) and T1566 (Phishing) as attackers can leverage the cleartext exposure to gather intelligence for more sophisticated attacks, while also enabling passive data collection through network monitoring. Organizations should also implement network segmentation and encryption monitoring to detect potential exploitation attempts, ensuring that the fundamental security assurances of end-to-end encrypted messaging systems remain intact.