Convicted national security leaker Chelsea Manning was found guilty Tuesday of violating prison rules and will receive three weeks of recreational restrictions at the Kansas military prison where Manning is serving a 35-year sentence.

The transgender Army private, formerly known as Bradley Manning, was accused of having a copy of Vanity Fair with Caitlyn Jenner on the cover and an expired tube of toothpaste, among other things. Attorney Chase Strangio of the American Civil Liberties Union, said in a news release that Manning was convicted of all charges after a closed four-hour disciplinary board hearing where no counsel was present.

Manning received 21 days of recreational restrictions limiting access to the gym, library and outdoors. The maximum possible penalty was indefinite solitary confinement.

The U.S. Army has declined to release any information on the results of the hearing, citing the Privacy Act of 1976. The military said in a statement last week that it is committed to "a fair and equitable process," and called such proceedings "a common practice in correctional systems to hold prisoners accountable to facility rules."

The prison infractions include possession of prohibited property in the form of books and magazines while under administrative segregation; medicine misuse over the toothpaste; disorderly conduct for sweeping food onto the floor; and disrespect. All relate to alleged misconduct on July 2 and 9.

"When I spoke to Chelsea earlier today she wanted to convey the message to supporters that she is so thankful for the thousands of people from around the world who let the government know that we are watching and scrutinizing what happens to her behind prison walls," Strangio said.

Strangio credited public support for keeping Manning out of solitary confinement. Petitions signed by 100,000 people were delivered Tuesday to the U.S. Army by digital rights group Fight for the Future and others.

In addition to the recreational restrictions, the convictions that are now on Manning's record could be cited in future hearings concerning parole or clemency, which could delay the transition to a less restrictive custody status, Strangio said.

The intelligence analyst was convicted in 2013 of espionage and other offenses for sending more than 700,000 classified documents to WikiLeaks while working in Iraq. Manning is jailed at Fort Leavenworth for leaking reams of war logs, diplomatic cables and battlefield video to the anti-secrecy website in 2010.