Title: Timestamp Manipulation with Signature Wrapping
Announced: October 11, 2021
Fixed in: LibreOffice 7.0.6/7.1.2
LibreOffice supports digital signatures of ODF documents and macros within documents, presenting visual aids that no alteration of the document occurred since the last signing and that the signature is valid.
An Improper Certificate Validation vulnerability in LibreOffice allowed an attacker to modify a digitally signed ODF document to insert an additional signing time timestamp which LibreOffice would incorrectly present as a valid signature signed at the bogus signing time.
Thanks to NDS of Ruhr University Bochum for discovering and reporting this problem.
Thanks to Michael Stahl of allotropia software GmbH for solving this problem.