The buying back of a company's shares is a legal function that must be accompanied with a filing explaining exactly what is going to happen, how many shares are involved, etc. Anything else is stock manipulation, which would be illegal. The company itself can absolutely not buy shares without that filing.
"In addition to meeting these four requirements, companies are also required to disclose certain information quarterly on Form 10-Q, and annually on Form 10-K. The company must provide a table showing several month-by-month statistics. These statistics include:
The total number of shares purchased The average price paid per share The total number of shares purchased under publicly-announced repurchase programs The maximum number of shares (or maximum dollar amount) it can repurchase under these programs" There will be no share buyback until the company is current in its reporting.