The singer, who left the band in 2005 to pursue a solo career, is now listed on the official EU Trademark website as an owner of the Sugababes title.
Buena wrote on her Facebook page: "I won the official name of the Sugababes now!!! I deserve this! I'm over the moon!" She later added: "in tears feels like a dream (sic)."
However, it appears Buena has only won the rights to the name for a limited number of products, securing the rights to goods listed under Class 16 alone.
According to the EU Trademark website, Buena now owns Sugababes rights to "paper, cardboard and goods made from these materials, not included in other classes; namely stationery, paper gift wrap and paper gift wrapping ribbons".
Buena co-founded the Sugababes with original members Siobhan Donaghy and Keisha Buchanan, who left the group in 2001 and 2009 respectively.
The current lineup - Heidi Range, Amelle Berrabah and Jade Ewen - are due to release their new single 'Freedom' on September 25 and the band's eighth studio album later this year.
Buena had previously been involved in a long-running court battle to acquire ownership of the group's name.
Last year, Buena insisted that she wasn't bothered by the Sugababes, adding: "It's so silly. I'm in two minds about music in general."
Watch the original Sugababes lineup perform 'Overload' live below: