AC Milan have held talks with Chelsea over the transfer of Fernando Torres, according to Sky sources.
Mehdi Benatia has completed his move to Bayern Munich by signing a five-year contract after a successful medical.
Seaborne has won three and drawn one of the four matches he has played in since making the temporary move to The Valley.
The 25-year-old was forced to sit out the final match of his original loan spell, last Saturday's 2-2 draw against Brighton.
But Seaborne will get the chance to extend his unbeaten run in the Charlton team after a fresh deal was struck.