CVE-2018-6871 in LibreOffice
Summary
by MITRE
LibreOffice through 6.0.1 allows remote attackers to read arbitrary files via =WEBSERVICE calls in a document, which use the COM.MICROSOFT.WEBSERVICE function.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/18/2024
CVE-2018-6871 represents a critical server-side request forgery vulnerability in LibreOffice versions up to 6.0.1 that enables remote attackers to access arbitrary files on the system through malicious document manipulation. This vulnerability specifically exploits the WEBSERVICE function within LibreOffice's spreadsheet component, which allows the application to make HTTP requests to external resources. The flaw occurs when a document contains a formula referencing the COM.MICROSOFT.WEBSERVICE function, enabling attackers to craft malicious spreadsheets that can retrieve data from internal network resources or local files that would normally be inaccessible from the internet. The vulnerability stems from insufficient input validation and improper sandboxing of external resource access within the document processing engine. This issue falls under CWE-918, Server-Side Request Forgery, which is a well-documented class of vulnerabilities where applications fetch resources from untrusted sources without proper validation. The attack vector is particularly concerning because it can be delivered through standard document attachments, making it an effective method for initial access and lateral movement in enterprise environments. When a user opens a malicious document, LibreOffice executes the WEBSERVICE function and attempts to connect to the specified URL, potentially allowing access to internal resources such as file shares, database servers, or other network services that are normally protected by firewalls or network segmentation. The operational impact extends beyond simple file access, as attackers can leverage this vulnerability to gather sensitive information, perform reconnaissance, or establish persistence within the network. The vulnerability is particularly dangerous in corporate environments where LibreOffice is commonly used for business documents, as it can be exploited through social engineering campaigns targeting employees with malicious attachments. According to ATT&CK framework, this vulnerability maps to T1190 - Exploit Public-Facing Application, where attackers use compromised applications to gain access to internal systems. The risk is amplified by the fact that LibreOffice is widely deployed across various operating systems including Windows, macOS, and Linux, making the attack surface extensive. Organizations using LibreOffice versions prior to 6.0.2 should immediately implement mitigations such as disabling external resource access, implementing strict network segmentation, and deploying application control measures to prevent execution of malicious formulas. The vulnerability also highlights the importance of regular software updates and maintaining current security patches to protect against known exploits. Additionally, network monitoring should be enhanced to detect unusual outbound connections from office applications, particularly those attempting to access internal resources. Security teams should also consider implementing sandboxing mechanisms for document processing and establishing clear policies for handling external document attachments. The remediation process requires careful consideration of business continuity needs while ensuring that the vulnerability is properly addressed through official patches from The Document Foundation. Organizations should also conduct security awareness training to help employees recognize potentially malicious document attachments that could exploit this vulnerability. The broader implications of this vulnerability demonstrate the critical need for robust input validation and secure coding practices in office productivity applications, as these tools are frequently targeted by attackers seeking to gain unauthorized access to corporate networks through seemingly benign document interactions.