Last month, Yahoo disclosed a massive data breach in 2014 that affected at least 500 million of its email accounts.
According to Reuters, Verizon's general counsel said on Thursday that the company has a "reasonable basis" to believe the hack represents a material impact that could allow it to withdraw from the deal to buy the company.
Verizon reports results on Oct. 20.
Companies that are being acquired do not typically hold earnings calls with analysts.