A contractual teacher hurled his slipper towards the Chief Minister, but it fell some distance from the dais where Kumar was being garlanded by his supporters, the sources said.
The security personnel tried to identify the protester, but he escaped by joining among audience gathered there, they said.
The Chief Minister's public meeting proceeded without any more interruption amid tight security, sources said.
Earlier, the police detained 23 contractual teachers for allegedly planning to sabotage Kumar's 'Adhikar yatra' in the district.
The detainees have been lodged at Madhepura police station, Deputy Superintendent of Police (DSP) H S Dwivedi said.
It was for the third time in the past fortnight that the CM has either being shown slippers or the same hurled in his direction, after the contractual teachers did so in Betiah and Darbhanga.
Unfazed by the protests, Kumar said, he would continue to fight for the special category status to Bihar for betterment of the state.