In an interview on "Squawk Box," Decker explained that she does not know the ins and outs of the Yahoo-Verizon merger deal and when Mayer's pay package was negotiated.
"Given what happened in the performance of the company, it seems on the egregious side," Decker said.
According to reports, Mayer stands to make $186 million in the event that Yahoo sells its internet business to Verizon, though that total could change based on Yahoo's stock price.
Yahoo did not immediately respond to a CNBC request for comment.
Verizon and Yahoo are closing in on their $4.4 billion merger deal, which was first in July and has been delayed as Yahoo assesses the fallout from two data breaches disclosed last year. Yahoo agreed to cut the price tag of its acquisition deal following the discovery of the cyberattacks.
Verizon, the No. 1 U.S. wireless carrier, had been trying to persuade Yahoo to amend the terms of the agreement. Under the new terms, the companies will split cash liabilities related to some government investigations and third-party litigation related to the breaches.
Yahoo shareholders will vote on the deal on June 8.
—Reuters contributed to this report.
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