LibreOffice and OpenOffice have launched the updates to address a vulnerability that makes it possible for a threat actor to manipulate documents to come assigned by authenticating sources.
Although the severity of the bug is classified as balanced, the implications could be dire. The digital signature used in document macros are meant to help the user verify that document has not been warned and can be trusted.
Discovery of the Flaw
“Permitting anyone to sign macro-ridden documents them, and makes them appear as trustworthy, is an excellent way to trick users into running malicious code.”
The discovery of the flaw, which is tracked as CVE-2021-41832 for OpenOffice, was the work of four researchers at the Ruhr University Bochum.
A similar bug affects LibreOffice, which is a fork of OpenOffice generated from the main project over a decade ago, and their project is addressed as CVE-2021-25635.
What is the Risk to be addressed?
If you’re using either of the open-source office suites, you’re advised to upgrade to the latest available version immediately. For OpenOffice, that would be 4.1.10 and later, and for LibreOffice, 7.0.5 or 7.1.1 and later.
Since neither of these two applications offers auto-updating, you should do it manually by downloading the latest version from the respective download centers – LibreOffice, OpenOffice.
If you’re using Linux and the aforementioned versions aren’t available on your distributions package manager yet, you are advised to download the “deb”, or “rpm” package from the Download center or build LibreOffice from the source.
If updating to the latest version is not possible for any reason, you can always opt to completely disable the macro features on your office suite, or avoid trusting any documents containing macros. To set macro security on LibreOffice, go to Tools < Options < LibreOffice < Security, and click on ‘Macro Security.
In the new dialog, you may select among four distinct levels of security, with High or Very High being the recommended options.
In case you are still running an old and vulnerable version, you should not rely on the authenticated list functionality as an invalid signature algorithm could still make a fortified document appear as it comes from a trusted source.
