CVE-2026-62642 in Roundcube
Summary
by MITRE • 07/14/2026
In Roundcube Webmail before 1.6.17 and 1.7.x before 1.7.2, an infinite loop was discovered in the TNEF decoder, which may lead to denial of service upon opening an email with a TNEF attachment.
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Analysis
by VulDB Data Team • 07/14/2026
The vulnerability exists within Roundcube Webmail's handling of TNEF (Transport Neutral Encapsulation Format) attachments, specifically affecting versions prior to 1.6.17 and 1.7.x prior to 1.7.2. This issue represents a classic denial of service condition where maliciously crafted TNEF attachments can trigger an infinite loop in the decoding process. The TNEF format is commonly used by Microsoft Outlook to encapsulate rich text formatting and embedded objects within email messages, making it a legitimate attachment type that users might encounter in normal email operations.
The technical flaw manifests as an infinite loop within the TNEF decoder implementation, where the parsing logic fails to properly terminate execution when encountering malformed or specially crafted TNEF data structures. This occurs during the processing of TNEF attachments when the application attempts to decode nested objects and properties without proper boundary checks or loop termination conditions. The vulnerability is particularly dangerous because it can be triggered simply by opening an email message containing a malicious TNEF attachment, requiring no additional user interaction beyond normal email reading operations.
From an operational impact perspective, this vulnerability allows attackers to perform denial of service attacks against Roundcube Webmail users by sending specially crafted emails that will cause the application to consume excessive CPU resources or become unresponsive. The infinite loop effectively blocks the web server process handling the affected email, preventing legitimate users from accessing their inbox or processing other emails until the system is restarted or the problematic message is manually removed. This represents a significant availability risk for organizations relying on Roundcube as their primary webmail solution.
The vulnerability aligns with CWE-835, which specifically addresses infinite loops in software implementations where loop termination conditions are improperly handled or missing entirely. From an ATT&CK framework perspective, this maps to T1499.004 - Endpoint Denial of Service, where adversaries leverage application-level vulnerabilities to disrupt service availability. The attack vector requires minimal privileges as it operates through standard email delivery mechanisms, making it particularly concerning for enterprise environments where email is a critical business function.
Mitigation strategies should prioritize immediate patching to versions 1.6.17 or 1.7.2 and later, which contain the necessary fixes for the TNEF decoder loop conditions. Organizations should also implement email filtering rules that quarantine or reject TNEF attachments if they are not required for business operations, though this approach may impact legitimate email communications. Network-level monitoring should be enhanced to detect abnormal CPU usage patterns that might indicate exploitation attempts. Additionally, implementing rate limiting on email processing and establishing proper resource limits on web server processes can help contain the impact if an attack does occur.