I think someone is definitely helping the North Koreans with their missile technology, but blaming Ukraine sounds like a Russian information operation:
Ukraine’s top diplomat in Seoul on Thursday denied allegations that North Korea might have obtained rocket engines used in its recently tested long-range missiles from Ukraine.
Charge d’Affaires Taras Fedunkiv, the acting Ukrainian ambassador to Seoul, still suspected that North Korea could not have been able to advance its missile technology “without outside help,” calling for an international probe to find “who was responsible.”
“The production lines for building these types of rockets in Ukraine were decommissioned in 1992. The expertise cannot be carried in the heads of rogue scientists. The instructions are included in complex manuals locked in top-security facilities guarded by our security forces,” he said in a written interview with Yonhap News Agency, citing Ukraine’s Foreign Minister Pavlo Klimkin’s recent op-ed in The New York Times.
“Not only would it be virtually impossible for criminals to access these manuals, but also any effort could not go unnoticed by our government,” he added.
Citing a study by Michael Elleman, a missile expert at the International Institute for Strategic Studies, the New York Times reported on Aug. 14 that North Korea could have got its hands on technology needed for the success of the recent missile launches through black market purchases of rocket engines from Ukraine. [Yonhap]
You can read more at the link, but I would not be surprised if it was the Russians helping the North Koreans master their long range rocket technology.