CVE-2025-64401: Apache OpenOffice Auth Bypass Vulnerability

CVE-2025-64401 Overview

A Missing Authorization vulnerability has been identified in Apache OpenOffice that allows attackers to craft malicious documents capable of loading external links without user consent. The vulnerability specifically affects how OpenOffice handles "floating frames" linked to external files, bypassing the expected security prompt that should alert users before loading external content.

When a user opens a specially crafted document containing floating frames, the application automatically loads the contents of those frames from external sources without requesting permission. This behavior circumvents security controls designed to protect users from potentially malicious external content loading.

Critical Impact

Attackers can craft documents that automatically load external content without user consent, potentially enabling data exfiltration, tracking, or delivery of malicious payloads through trusted document workflows.

Affected Products

• Apache OpenOffice through version 4.1.15
• All Apache OpenOffice installations prior to version 4.1.16

Discovery Timeline

• 2025-11-12 - CVE CVE-2025-64401 published to NVD
• 2025-11-13 - Last updated in NVD database

Technical Details for CVE-2025-64401

Vulnerability Analysis

This vulnerability (CWE-862: Missing Authorization) stems from Apache OpenOffice's failure to enforce proper authorization checks when processing floating frame elements within documents. Floating frames are document components that can reference and display content from external URLs. Under normal security conditions, the application should prompt users before fetching any external resources, allowing them to make informed decisions about whether to trust the content source.

The issue manifests when OpenOffice parses documents containing floating frame elements with external URL references. The authorization check that should trigger a user prompt is bypassed, allowing the external content to load automatically. This represents a significant security control failure as it removes the user's ability to consent to external connections.

It's worth noting that LibreOffice previously reported this same vulnerability class as CVE-2023-2255, indicating this is a known issue pattern within OpenDocument format implementations.

Root Cause

The root cause is a Missing Authorization vulnerability (CWE-862) in Apache OpenOffice's floating frame handling code. The application fails to implement proper authorization checks before initiating network requests for externally linked frame content. This allows the security prompt mechanism to be bypassed entirely, creating a pathway for silent external resource loading.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction beyond opening the malicious document. An attacker can exploit this vulnerability through the following approach:

1. Document Crafting: The attacker creates an OpenOffice document containing floating frame elements that reference attacker-controlled external URLs
2. Document Distribution: The malicious document is distributed to victims through email attachments, file sharing, or other document delivery mechanisms
3. Silent Execution: When the victim opens the document in a vulnerable version of Apache OpenOffice, the floating frames automatically load content from the external URLs without displaying a security prompt
4. Impact Realization: The attacker can leverage this behavior for user tracking, network reconnaissance, credential harvesting through NTLM relay attacks, or delivery of additional malicious content

The vulnerability exploits the trust users place in document files and the expectation that office applications will warn them before making external network connections.

Detection Methods for CVE-2025-64401

Indicators of Compromise

• Unexpected outbound network connections originating from soffice.bin or related OpenOffice processes
• Documents containing suspicious floating frame elements with external URL references
• Network logs showing connections to unknown or suspicious external domains immediately after document opening events
• HTTP/HTTPS requests from OpenOffice processes to external servers that were not explicitly authorized by users

Detection Strategies

• Monitor network traffic from Apache OpenOffice processes for unexpected external connections
• Implement document scanning solutions that can analyze ODF files for floating frame elements with external URL references
• Deploy endpoint detection rules to alert on OpenOffice processes initiating network connections to untrusted domains
• Configure web proxy logging to correlate document open events with subsequent outbound requests

Monitoring Recommendations

• Enable verbose logging for Apache OpenOffice to track document loading events and external resource requests
• Implement network segmentation to restrict OpenOffice processes from accessing untrusted external resources
• Deploy SIEM rules correlating process execution events with network connection attempts
• Configure alerts for bulk document scanning or processing operations that may indicate reconnaissance activity

How to Mitigate CVE-2025-64401

Immediate Actions Required

• Upgrade Apache OpenOffice to version 4.1.16 or later immediately
• Audit recently opened documents for suspicious floating frame content
• Review network logs for potential exploitation attempts during the vulnerable period
• Implement temporary network restrictions for OpenOffice processes until patching is complete

Patch Information

Apache has released version 4.1.16 of OpenOffice which addresses this vulnerability. Users are strongly recommended to upgrade to this version to remediate the issue. Additional details are available through the Apache Security Mailing List and the official OpenOffice CVE-2025-64401 advisory.

Workarounds

• Disable or restrict network access for Apache OpenOffice processes at the firewall or host level until patching can be completed
• Configure endpoint protection to block outbound connections from soffice.bin and related OpenOffice executables
• Implement document sandboxing to isolate potentially malicious documents from network resources
• Train users to exercise caution when opening documents from untrusted sources

# Block OpenOffice outbound connections (Linux iptables example)
# Identify OpenOffice user or run with restricted permissions
iptables -A OUTPUT -m owner --cmd-owner soffice.bin -j DROP