In a pre-Christmas speech to the officials of the Roman Curia, Francis kept the season's greeting to a minimum, choosing instead to ask prelates to make "a real examination of conscience."
Francis then listed 15 "illnesses" he said they were prey to, including the "terrorism" of gossip, which he called a "cowardly" disease which could kill the reputation of a colleague "in cold blood."
Top of the list was the fault of feeling "immortal, immune or even indispensable," which Francis said could be remedied by a visit to a cemetery to see the graves of those who once felt immortal.
Francis also slammed prelates for showing off, accumulating wealth and leading double lives, which he said could lead to "existential schizophrenia."
Since his election last year, Francis has named a panel of eight cardinals to help him end mismanagement and infighting among Vatican bureaucrats, which was exposed by the leaking of letters addressed to his predecessor, Pope
"I have never seen a Christmas speech like this; this felt more like Lent," said Maria Antonietta Calabro, a Vatican specialist at Italy's Corriere della Sera newspaper. "Francis was elected to clean up the Curia and he is returning to this theme and strongly reasserting his authority."
Some of Francis' 15 points felt like a guide to good management. He advised his audience to work as a team to avoid sounding like "an orchestra that makes a racket" and to avoid pursuing inflexible plans and turning into "procedural machines" by overworking.
Forming small cliques was "a cancer," he added, while worshiping a superior to gain promotion was condemned. Francis also complained about people with a "funereal face" who want to be taken seriously by treating others with "rigidity, hardness and arrogance."
"Let's not lose that joyous spirit, full of humor and even self-irony, that makes us likable, even in difficult situations," he said.
Marco Tosatti, a Vatican expert at the La Stampa newspaper, played down the seriousness of the speech. "These are things that popes have said before, even if Francis did the whole list," he said.
But some points appeared to single out individual cardinals for chastisement. Francis attacked those who accumulate possessions and told the story of a Jesuit who packed a truck full of books and presents when he moved house.
Calabro said the tale appeared to be a reference to Cardinal Tarcisio Bertone, the former Vatican secretary of State who has been criticized for renovating and moving into a large apartment at the Vatican, close to Francis' small quarters.
Francis also attacked those who "discredit others, even in newspapers and magazines" to build their own power, even if they claim they are doing so "in the name of justice and transparency."
Australian Cardinal George Pell, who was tasked by Francis with giving order to Vatican finances, recently wrote an article for a Roman Catholic publication claiming he had found millions of euros unaccounted for only to have Vatican officials deny funds were concealed.
"It looks like Francis is referring to Pell, which is ironic because Pell is his man," said Calabro.
Francis' harsh words for Curia staff contrasted with a speech of gratitude he also gave Monday to lay Vatican staff including gardeners and cleaners.
Thanking them for their work, he asked "forgiveness for the shortcomings of my colleagues and myself, as well as for some scandals, which do great harm," he told them. "Forgive me."