The incident was related to intergang tensions within the unit, the summary of facts said.
Brown picked up an empty plastic rubbish bin and took it to the shared kitchenette, where he filled it with about 10 litres of boiling water from the Zip water dispenser.
He then carried the bucket of water up a nearby stairwell to cell 27, where the victim was trying to intervene in a physical altercation between another group of Nomads and the Black Power member whose cell it was.
"The defendant raised the bin and threw boiling water directly over the victim's right side, hitting his neck, arms and torso," the summary said.
"The temperature of the water caused instant redness, peeling, and blistering to the right half of the victim's body."
Corrections staff then intervened and segregated all the parties following the incident.
The victim suffered "severe" burns and needed surgery. The court did not have any further information on the victim's injuries.
Judge Patrick Grace told Brown there was a requirement in prison environments for people to "act appropriately and to not act like animals".
He said this was a case of "extreme violence".
Judge Grace sentenced Brown to two years and one month in prison.
Corrections' chief custodial officer Neil Beales said prisoners in medium-high security units have access to hot water through dispensers, and can only access them at specific times.
"Prisoners can fill a thermos that meets our size regulations with hot water if they need access to hot water outside of these specified times."
The water is normally 70C, but on that day a fault in the system meant the water was coming out at 90C. The boiling point of water is 100C.
"As soon as we were aware of the fault we contacted our facilities maintenance contractor and requested they urgently fix the issue."
They now carry out regular checks of all hot water dispensers at the prison to ensure this cannot happen again.
"Immediately after the assault occurred, staff responded to bring the situation under control, apply first aid to the victim, and call an ambulance."
Prisoners often went to "extreme lengths" to harm staff or other prisoners, Beales said.
"Over 80 per cent of the prison population have convictions for violence in their offending histories and more than 90 per cent have a lifetime diagnosis of a mental health or substance abuse disorder."
Thirty-five per cent also have gang affiliations, "which is a known predictor of violence".
"The reality is the threat of violence is something we cannot eliminate entirely, but we are committed to doing everything possible to minimise this risk and provide the safest environment possible for staff and prisoners."
It's not the first time a prisoner has thrown boiling water over another inmate in Rimutaka Prison.
In 2019 Stephen Roger Williams - who murdered his stepdaughter Coral Burrows while high on meth - threw a 1-litre flask of boiled water over another inmate then stabbed him multiple times.
He was sentenced to preventive detention for attempted murder.
