Who are Jannes and Jambres in 2 Timothy 3:8?

As Jannes and Jambres opposed Moses, so these people, of corrupt mind and counterfeit faith, also oppose the truth. (2 Tim 3:8 NRSV)

8. Ἰαννῆς καὶ Ἰαμβρῆς] (or possibly Μαμβρῆς, which is found in the Western texts and in the Talmud). An ad hominem illustration. They are fond of their Jewish myths and genealogies: well, the nearest analogy to themselves to be found there is that of magicians whose folly was exposed. ὃν πρόπον may perhaps imply similarity of method, that these teachers used magic arts like the Egyptian magicians; cf. γόητες 13 and Acts 19:19. The reference is to Ex 7:11, 9:11. The names are not found in O.T., Philo, or Josephus, but in slightly different forms in late Jewish Targums, one perhaps as early as the first Christian century (Schechter, Documents of Jewish Sectaries, i. p. 5); in heathen writers (Pliny, Hist. Nat. xxx. 1. 11; Apuleius, Apol. c. xc.), and in several Christian Apocryphal writings, e.g. Evang. Nicodemi, c. 5). Origen twice (ad Matth. 27:9 23:37) refers to an Apocryphal book with the title “Jannes et Mambres.” The names are apparently Semitic, perhaps meaning “the rebel” and “the opponent” (so Thackeray, The Relation of St. Paul to Contemporary Jewish Thought, pp. 216–21). For fuller details, cf. Schürer, H.J.P. (Eng. tr.) ii. 3. 149, Wetstein, Holtzmann, Dibelius, and W.-H. Notes on Select Readings, ad loc.

Lock, W. (1924). A critical and exegetical commentary on the Pastoral epistles (I & II Timothy and Titus) (p. 107). Edinburgh: T&T Clark.