CVE-2013-5035 in HtmlCleaner
Summary
by MITRE
Multiple race conditions in HtmlCleaner before 2.6, as used in Open-Xchange AppSuite 7.2.2 before rev13 and other products, allow remote authenticated users to read the private e-mail of other persons in opportunistic circumstances by leveraging lack of thread safety and performing a rapid series of (1) mail-sending or (2) draft-saving operations.
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Analysis
by VulDB Data Team • 03/18/2019
The vulnerability identified as CVE-2013-5035 represents a critical race condition flaw in HtmlCleaner library versions prior to 2.6, which was extensively deployed in Open-Xchange AppSuite 7.2.2 before revision 13 and numerous other applications. This security weakness stems from inadequate thread safety mechanisms within the HtmlCleaner component, creating exploitable conditions that enable authenticated attackers to gain unauthorized access to private email communications. The vulnerability manifests when attackers leverage concurrent operations to manipulate the application state during critical processing phases, specifically targeting the mail-sending and draft-saving functions that lack proper synchronization controls. The race condition occurs because multiple threads can simultaneously access and modify shared resources without appropriate locking mechanisms, allowing malicious actors to intercept or read messages intended for other users.
The technical exploitation of this vulnerability requires an authenticated user account within the target system, as the attack operates within the legitimate user context but leverages the inherent concurrency flaws in the HtmlCleaner library. Attackers must carefully time their operations to perform rapid series of mail-sending or draft-saving activities, taking advantage of the window of opportunity created by the lack of proper thread synchronization. This timing aspect makes the vulnerability particularly challenging to detect and prevent, as it relies on specific operational conditions and system timing rather than direct exploitation of network protocols or authentication mechanisms. The flaw specifically affects the application's ability to handle concurrent operations safely, creating a scenario where data integrity cannot be guaranteed during critical processing phases.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally compromises the confidentiality assurances expected in email communication systems. When successful, attackers can read private emails intended for other users, potentially accessing sensitive business information, personal data, or confidential communications that should remain protected. The opportunistic nature of the attack means that the vulnerability can be exploited under specific conditions rather than requiring constant exploitation, but the potential damage remains significant given the sensitive nature of email communications. This type of vulnerability directly violates the principle of least privilege and can lead to cascading security issues if attackers use the compromised information to launch further attacks or gain additional system access.
Organizations should implement immediate mitigations including updating to HtmlCleaner version 2.6 or later, which includes proper thread safety mechanisms and synchronization controls. Additionally, system administrators should consider implementing additional access controls and monitoring for unusual patterns of mail-sending or draft-saving operations that might indicate exploitation attempts. The vulnerability aligns with CWE-362, which describes race conditions in software systems, and represents a classic example of how insufficient concurrency control can create security weaknesses. From an ATT&CK perspective, this vulnerability could be categorized under privilege escalation and credential access techniques, as it allows attackers to bypass normal access controls through manipulation of shared resources. The remediation process should include comprehensive testing to ensure that the updated HtmlCleaner library functions correctly within the specific application environment while maintaining all existing functionality and user experience requirements.