Sky Sports are linking us with one time Reading midfielder Kalifa Cisse (he also played for Bristol City). The 29-year old has been playing in the States with New England Revolution where apparently he has done well. He has a release clause in his contract which allows him to return for a nominal fee.
However, according to Sky a number of other clubs are interested including Watford, Millwall and Middlesbrough.
To me this looks a bit like an agent trying to drum up interest by mentioning any likely club that comes into his head, so it is probably not a very likely prospect. Certainly, there is no verifiable Charlton interest.