CVE-2015-1641: Microsoft Office Memory Corruption Vulnerability

CVE-2015-1641 is a memory corruption vulnerability in Microsoft Office that stems from improper handling of rich text format (RTF) files in memory. An attacker who successfully exploits it can achieve remote code execution in the context of the current user, which can lead to further compromise of the workstation and any resources that user can reach. IT and security teams should treat this as a high-priority Office client risk and confirm exact scope and fixes against the vendor advisory.

CISA notes that the required action is to apply updates per vendor instructions. Public detail on ransomware use is not documented for this CVE; focus on standard remote-code-execution response and hardening for the Office document-handling path.

How it works

This issue is classified under CWE-399 (resource management errors). In plain terms, Office fails to manage memory correctly when processing certain RTF content. Memory corruption of this class can let an attacker influence program control flow so that attacker-controlled code runs with the privileges of the logged-on user.

Abuse typically involves delivering a crafted RTF file—commonly as an email attachment, a downloaded document, or a file opened from a share or web location—and enticing the user to open it in a vulnerable Office application. Because execution occurs as the current user, the impact depends on that user’s rights, running security controls, and whether additional techniques are used to escalate or move laterally. Exact exploit mechanics and any proof-of-concept details are not provided here; treat any RTF-borne Office memory-corruption pattern as in-scope and verify behavior against the vendor advisory.

Am I affected? How to find it in your systems

Microsoft Office is commonly installed on end-user Windows workstations, VDI/session hosts, and some servers that process documents. Inventory every system that has Office components capable of opening or previewing RTF or related rich-text content.

• Use software inventory (SCCM/ConfigMgr, Intune, vulnerability scanners, or agent-based asset tools) to list installed Office editions and build levels.
• Compare those builds to the fixed versions listed in the Microsoft advisory for CVE-2015-1641; do not assume version ranges from secondary sources.
• Check whether users open RTF or Office documents from email, web downloads, or untrusted shares; preview panes and automatic conversion features can increase exposure.
• Review endpoint and email telemetry for unusual Office process behavior after document open (child processes, unexpected network connections, or crashes tied to RTF handling). Crash dumps or Windows Error Reporting events around Office when opening RTF may be worth investigating, but absence of crashes does not rule out successful exploitation.
• Confirm protected-view, Attack Surface Reduction, and application-control posture on endpoints that handle untrusted documents.

How to remediate

Patch first. Apply the Microsoft updates specified for CVE-2015-1641 exactly as described in the vendor advisory and your normal change process. CISA’s required action is to apply updates per vendor instructions.

• Deploy the relevant Office security updates through your enterprise patch channel and verify installation on all inventoried endpoints.
• After patching, validate that previously vulnerable builds are no longer present and that Office still functions for legitimate RTF/document workflows.
• Reinforce least privilege so that even successful user-context code execution has limited blast radius (standard user accounts, limited local admin, credential guard where applicable).
• Ensure email and web gateways strip or sandbox risky document types, and keep endpoint detection and response (EDR) content current so post-exploitation activity is more visible.

If you can't patch immediately

Reduce the attack surface until the vendor update can be applied everywhere.

• Block or quarantine untrusted RTF and Office attachments at the mail gateway; prefer sandbox detonation for documents from external senders.
• Disable or restrict automatic preview and conversion features that parse RTF without explicit user action, where business needs allow.
• Use application control or Attack Surface Reduction rules to limit Office applications from creating child processes or writing executable content—confirm rule compatibility with your Office deployment.
• Segment user workstations from high-value servers and sensitive data stores; require additional controls for access to admin or crown-jewel systems.
• Increase monitoring on Office processes for anomalous behavior and alert on suspicious follow-on activity until patching is complete.
• Virtual patching via endpoint or network controls may help for known exploit patterns, but it is not a substitute for the vendor fix; confirm any signatures or rules against current threat intelligence and the advisory.

If your data may have been exposed

Actively exploited remote-code-execution flaws in desktop productivity software frequently precede broader intrusion and data theft. If you have indicators that this vulnerability was used in your environment, follow your incident-response plan: isolate affected hosts, preserve evidence, reset credentials that may have been exposed, and assess lateral movement and data access. As a general hygiene step, users and administrators can run a free exposure scan of their email addresses against known breach datasets to see whether their identities already appear in public breach collections, then prioritize password changes and MFA accordingly.