Tuesday, June 28, 2016

Vulnerability Spotlight: LibreOffice RTF Vulnerability

Vulnerability discovered by Aleksandar Nikolic of Cisco Talos.

Talos is disclosing the presence of CVE-2016-4324 / TALOS-2016-0126, a Use After Free vulnerability within the RTF parser of LibreOffice. The vulnerability lies in the parsing of documents containing both stylesheet and superscript tokens. A specially crafted RTF document containing both a stylesheet and superscript element causes LibreOffice to access an invalid pointer referencing previously used memory on the heap. By carefully manipulating the contents of the heap, this vulnerability can be able to be used to execute arbitrary code. This vulnerability requires user interaction to open the file.

Rich Text Format (RTF) was designed as a cross platform format for interchanging documents. Although the format standard has not evolved since 2008, the format remains widely supported by word processing suites. Attackers have previously exploited RTF parser vulnerabilities in MS Office, and used RTF files as a vector for embedding other malicious objects. Exploiting vulnerabilities such as these requires the user to interact with and open the file in order to trigger the attack. Raising awareness of the existence of vulnerabilities such as these with users can help in reminding people not to open unexpected or suspicious emails or files. Although currently, we have no evidence to suggest that this vulnerability is being exploited in the wild.  We recommend that administrators upgrade systems to the latest version of LibreOffice to remove the vulnerability.

Snort rules: 39148, 39149

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