The Mishnah in Makkot 23a says
"All those liable to receive karet who were flogged in court were exempted from their karet
[...]
as it is stated with regard to one liable to receive lashes: “Then your brother shall be dishonored before you” (Deuteronomy 25:3) "
But Devarim 25:2-3 in fact says :
and it shall be, if the guilty one has incurred [the penalty of] lashes, that the judge shall make him lean over and flog him in front of him, commensurate with his crime, in number.
He shall flog him with forty [lashes]; he shall not exceed, lest he give him a much more severe flogging than these [forty lashes], and your brother will be degraded before your eyes.
So it seems like it's only speaking of one who committed a sin liable for lashes (and not for kares). How then can the Mishna use that pasuk to derive that one liable for kares is also exempted by lashes?