Remote Code Execution in JustSystems Ichitaro via Crafted Document

Successful exploitation allows arbitrary code execution in the context of the user who opens the malicious document. In practical intrusion activity, this enables initial compromise through spear-phishing or other document-delivery mechanisms, after which attackers can install malware, establish persistence, steal information, and use the compromised host as a foothold for further operations.

Until patches are fully deployed, reduce exposure by blocking or quarantining untrusted Ichitaro-compatible documents from email and web channels, especially in spear-phishing-prone environments. Limit execution of documents received from external sources, use application isolation or sandboxing for document handling where possible, and restrict user privileges to reduce post-exploitation impact. Additional mitigations include attachment detonation, content disarm and reconstruction, and heightened monitoring for suspicious child-process or payload execution originating from document-opening workflows.

Apply the vendor-provided security updates or upgrade affected Ichitaro products to versions that address CVE-2013-5990. Because multiple Ichitaro editions and release lines are affected, organizations should inventory all deployed Ichitaro installations, including government, professional, viewer, and portable variants, and ensure each is updated to a fixed release from JustSystems.