Boro coach Nick Greenwood said: "We're pleased that regular football has enabled Charlton to recall him.
"It says a lot for Carl's development while he's been at the club. We wish him all the best for the future."
The Finland under-19 international is due to be named in Charlton's squad for their Johnstone's Paint Trophy southern area semi-final at Brentford on Tuesday.
Source: BBC Sport
Source: BBC Sport