Ashley, who owns the Sport Direct retail chain, has owned the club since 2007.
He has been trying to offload it since September 2008, but has been unable to find anyone willing or able to pay the £80million he is asking. That would represent a £50.4m loss.
A statement released by the club late on Tuesday evening said Ashley was now “totally committed” to the Magpies and would put £20m into the club this week.
Hughton, 50, has been in caretaker charge of the first-team since the end of last season, when Alan Shearer’s eight-game run as manager failed to avoid relegation from the Premier League.
He told the club's official website: "I will be doing everything in my power to get the club back into the Premier League at the first time of asking.
"Having the unequivocal backing of the players has helped me enormously and I would also like to thank Colin Calderwood, Paul Barron and the rest of the backroom staff who have been tremendously supportive to me this season."
Two Championship clubs were knocked out of the Carling Cup in fourth round ties on Tuesday. Barnsley were beaten 2-0 by Manchester United, for whom Michael Owen and Danny Welbeck scored.
United had the former England defender Gary Neville sent off for an ugly lunge on the Barnsley winger Adam Hammill, a former Liverpool youngster, after 59 minutes.
The match was also marred by crowd trouble which saw 10 people arrested.
Blackburn Rovers comfortably saw off Peterborough United 5-2 at Ewood Park to leave Scunthorpe, who travel to face Manchester City on Wednesday, as the only Championship side left in the competition.
The Premier League sides Tottenham Hotspur, Aston Villa and Portsmouth are also through to the quarter-finals.