Forfeitures under 21 USC 853, upon conviction of certain crimes.
Under this provision, property vests in the US Government upon "the commission of the act giving rise to forfeiture under this section."
Any such property that is subsequently transferred to a person other than the defendant may be the subject of a special verdict of forfeiture and thereafter shall be ordered forfeited to the United States, unless the transferee establishes in a hearing pursuant to subsection (n) that he is a bona fide purchaser for value of such property who at the time of purchase was reasonably without cause to believe that the property was subject to forfeiture under this section
There is a 30 day window after the earlier of written notice (not mandatory) to third parties, or publication of notice of the order of forfeiture in which third parties may assert an interest. 21 USC 853(n)
if forfeited property, as a "result of any act or omission of the defendant— (A) cannot be located upon the exercise of due diligence; (B) has been transferred or sold to, or deposited with, a third party; (C) has been placed beyond the jurisdiction of the court; (D) has been substantially diminished in value; or (E) has been commingled with other property which cannot be divided without difficulty." Then, the court may order forfeiture of any other property of the defendant up to that value. 21 USC 853(p)
Garretson, FEDERAL CRIMINAL FORFEITURE: A ROYAL PAIN IN THE ASSETS, 18:1 Review of Law and Social Justice (2008)
For IRS/Treasury forfeitures, the government is authorized to warrant title to the purchaser and will sometimes issue Indemnification Agreements in favor of the title insurer pursuant to 31 USC 9705(l). We've previously been offered this form of indemnification agreement. Note that because of the difficulties of collecting from the Federal Government, an indemnity agreement doesn't substitute for having correctly followed all procedures in the forfeiture process.