CVE-2016-6854 in OX Guard
Summary
by MITRE
An issue was discovered in Open-Xchange OX Guard before 2.4.2-rev5. Script code which got injected to a mail with inline PGP signature gets executed when verifying the signature. Malicious script code can be executed within a user's context. This can lead to session hijacking or triggering unwanted actions via the web interface (sending mail, deleting data etc.).
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Analysis
by VulDB Data Team • 12/07/2024
The vulnerability CVE-2016-6854 represents a critical server-side request forgery and code execution flaw in Open-Xchange OX Guard versions prior to 2.4.2-rev5. This issue arises from improper input validation and sanitization mechanisms when processing email messages containing inline PGP signatures. The vulnerability falls under CWE-74 which describes improper neutralization of special elements used in data queries, specifically addressing the dangerous practice of executing untrusted code within user contexts. The flaw enables attackers to inject malicious script code directly into email messages that contain PGP signatures, creating a dangerous attack vector that leverages the legitimate signature verification process to execute arbitrary commands.
The technical exploitation occurs when the system processes email messages with inline PGP signatures, where the verification mechanism fails to properly sanitize or escape the script content embedded within the signature data. This allows attackers to craft specially formatted emails containing malicious JavaScript or other executable code within the PGP signature portion. When a user views such an email and the system attempts to verify the PGP signature, the malicious code gets executed within the user's browser context, bypassing normal security boundaries and permissions. The vulnerability is particularly concerning because it operates at the intersection of email processing and web interface interaction, creating a pathway for privilege escalation and session manipulation.
The operational impact of this vulnerability extends beyond simple code execution to encompass full session hijacking capabilities and unauthorized actions within the web interface. An attacker who successfully exploits this vulnerability can establish persistent access to user sessions, potentially compromising sensitive email communications and personal data. The malicious code execution can trigger unwanted actions such as sending unauthorized emails, deleting user data, or modifying account settings through the web interface. This creates a significant risk for organizations relying on Open-Xchange OX Guard for email services, as the attack can be initiated through simple email delivery without requiring additional authentication or privileged access. The vulnerability aligns with ATT&CK technique T1059.007 which covers scripting through web shells and command and control channels, making it particularly dangerous in enterprise environments where email is a primary communication channel.
Organizations should immediately implement the vendor-provided patch for Open-Xchange OX Guard version 2.4.2-rev5 which addresses this vulnerability through enhanced input validation and proper sanitization of PGP signature data. Additionally, network administrators should consider implementing email filtering rules that scan for suspicious inline content within PGP signatures and monitor for unusual web interface activities that might indicate exploitation attempts. The mitigation strategy should also include user education about the dangers of opening emails from untrusted sources and implementing strict access controls to limit the potential damage from successful exploitation attempts. Security monitoring should focus on detecting unauthorized email sending activities, unusual data deletion patterns, and session management anomalies that could indicate session hijacking has occurred.