The 36-year-old has scored 16 goals this season but was recently dropped by Seagulls manager Gus Poyet after claiming he had been placed on the transfer list.
Forster looks like he has played his last game for Brighton after signing for the Addicks until the end of the campaign, when he will be out of contract on the south coast.
Poyet said: "We always want to help players and we hope he goes to Charlton, scores some goals and helps them get promoted."
West Ham's Fry, 19, can play at centre-half or left-back and will provide some defensive cover at The Valley.
Both players are set to be added to the squad for Saturday's trip to Huddersfield.
Source: Team Talk
Source: Team Talk