https://en.wikipedia.org/wiki/Niger_uranium_forgeries

> In March 2003 [..] it reportedly took International Atomic Energy Agency (IAEA) officials only a matter of hours to determine that these documents were fake. IAEA experts discovered indications of a crude forgery, such as the use of incorrect names of Nigerien officials.

The CIA and foreign intelligence services did do some good work to try to correct that particular false narrative - something originally spread from Iran's intel service no less (which sounds a lot like the discredited 2016 'dossier' which came from questionable Russian sources). But they clearly didn't do enough. Probably because they were on the brink of getting new massive sweeping powers.

This one's my favourite CIA story from that era, just straight-up blatant disregard for the law with zero repercussions: https://en.wikipedia.org/wiki/2005_CIA_interrogation_videota...