Huntley was attacked in Frankland Prison in County Durham, where he is serving two life sentences for murdering schoolgirls Holly Wells and Jessica Chapman.
Reports suggested his throat had been slashed, but his condition is not believed to be life-threatening.
Huntley was convicted of murdering the girls, who were both 10, in December 2003 after they vanished from their homes in Soham, Cambridgeshire, in August 2002.
Yesterday's assault is not the first time Huntley has been attacked in prison. An inmate threw boiling water on him while he was on the health care wing at the high-security Wakefield Prison in September 2005.
HMP Frankland is a Category A high-security men's prison. In 2008, HM Inspectorate of Prisons raised concerns about violence at the jail. Last night the Ministry of Justice would not confirm if an investigation into the assault had been launched.
The murder of the two girls sent shockwaves across the country during the summer of 2002. Huntley, a caretaker at the secondary school in Soham, was given two life terms after being convicted of the girls' murders.
Girlfriend Maxine Carr, a teaching assistant, was jailed after being convicted of perverting the course of justice and has now been released from prison.