The 23-year-old defender is reportedly considering the offer, thought to involve a fee of approaching £8million.
Curbishley, whose team lost 3-0 in the Barclays Premier League at Manchester City on Sunday, told BBC Radio 5 Live: "The board have accepted the bid - he's not renegotiated his contract - and the decision was taken out of my hands.
West Ham have accepted a bid, thought to be in the region of £8million, from Sunderland for central-defender Anton Ferdinand
"I don't know where Anton is in terms of signing for Sunderland - but once the club accept the bid it moves on."
Ferdinand's current contract is set to end in 2010.
Curbishley, meanwhile, is hoping to sign a defender before the transfer window closes on September 1.
"We are thin on the ground," he said.
"If we lose another defender we will have to react to that."
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