New Defender's Study Bible Notes
2:17 canker. This could be an ulcer or any ulcerating sore, even a cancer.
2:17 Hymenaeus and Philetus. Hymenaeus means “singing man” and Philetus means “friendly man.” These names may well suggest the characters of these two blasphemers (see note on I Timothy 1:20). It is often true that the most effective subverters of God’s Word of truth are men who outwardly seem to be very smooth and charming (compare II Corinthians 11:13-15).
2:18 overthrow the faith. The implication of this phrase refers to those who were corrupting such vital truths as in Romans 6:5 and Colossians 3:1-3, in addition to denying the great promises of the future resurrection when Christ returns (e.g., I Thessalonians 4:16-17).