Vasco have reportedly submitted a proposal worth approximately €7 million (£6.1 million), falling €3 million (£2.6 million) short of the purchase option included in the player's loan agreement.
Nottingham Forest would prefer to begin negotiations from the €10 million (£8.7 million) figure already established in that arrangement, but recognise that securing the full amount could prove difficult.
According to RTI Esporte, Forest have yet to formally respond to the proposal, although the expectation is that they will initially turn it down.
The situation is nevertheless open to negotiation, with Forest willing to consider a lower figure if the financial terms are acceptable.
Cuiabano is currently on loan at Vasco, with his temporary arrangement due to expire in December. The 23-year-old has established himself in Brazil and is keen to remain in Rio de Janeiro rather than return to England.
Forest are reportedly not planning to incorporate him into their squad when he returns in January, meaning a permanent departure is the preferred solution.
The defender remains under contract at the City Ground until June 2029, giving Forest considerable control over his future. However, the club are aware that Vasco are unlikely to meet the full purchase-option figure.
There is also another consideration for Forest. Their difficult Premier League campaign could influence January recruitment, with the club expected to look at selective additions while attempting to generate funds through player sales.
Vasco believe there is room to negotiate the asking price downwards, although the difference between the two clubs' valuations remains significant.
The Brazilian side have also identified another potential opportunity involving a Forest player.
According to information from journalists close to Vasco, the club want to use the existing discussions over Cuiabano to explore a possible move for goalkeeper John Victor.
The former Botafogo goalkeeper has struggled to establish himself at Nottingham Forest and has fallen down the pecking order. Vasco believe they could take advantage of his situation to bring him back to Brazilian football.
John Victor has already attracted interest from other Brazilian clubs, with Vasco having previously explored the possibility of signing him.
Forest are reportedly willing to consider a permanent sale, although they would prefer a transfer fee of approximately €9 million (£7.8 million). They are not interested in another loan arrangement.
The goalkeeper has made only nine appearances since joining Forest in August 2025 and has yet to feature for the first team this season.
Vasco's interest in both players could therefore provide an opportunity to negotiate a double transfer, using the existing Cuiabano discussions to explore an agreement for John Victor as well.
There is, however, a difference between the reported valuations of Cuiabano. While the latest proposal is understood to be worth around €7 million, another report suggests Vasco would ultimately like to negotiate the figure down to approximately €6 million (£5.2 million).
For now, the €7 million proposal is the more firmly reported figure, and Forest have not accepted either valuation.
A double deal would suit Vasco as they look to strengthen their squad ahead of 2027, but the financial details will determine whether negotiations can progress.