ICBN Art 11:

Ex. 12. Cucubalus behen L. (1753) when transferred to Behen Moench was
legitimately renamed B. vulgaris Moench (1794) to avoid the tautonym "B.
behen". In Silene L., the epithet behen is unavailable because of the
existence of S. behen L. (1753). Therefore, the substitute name S.
cucubalus Wibel (1799) was proposed. This, however, is illegitimate since
the specific epithet vulgaris was available. In Silene, the correct name
of the species is S. vulgaris (Moench) Garcke (1869).