Wyo. Stat. § 4-10-507

(a) Subject to the rights of persons dealing with a fiduciary as provided in W.S. 4-10-1013, a creditor may file a claim against the assets of the trust or commence a judicial proceeding to contest the validity of a trust that was revocable at the settlor's death within the earlier of:

(i) Two (2) years after the settlor's death;

(ii) One hundred twenty (120) days after the first publication of a notice of the intent of the trustee to have the property of the settlor distributed as permitted under the terms of the trust. The notice shall be published once per week for two (2) consecutive weeks in a newspaper of general circulation in the county or counties where venue of the trust is properly established as provided in W.S. 4-10-204; or

(iii) One hundred twenty (120) days after known creditors have been mailed notice, by certified mail return receipt requested. The notice shall inform the creditor:

(A) Of the trust's existence;

(B) Of the trustee's name and address;

(C) That the creditor shall make all claims in writing to the trustee within one hundred twenty (120) days of the date of mailing of the notice; and

(D) That time allowed for commencing a proceeding to contest the validity of a trust or of the proposed distribution of the trustee is one hundred twenty (120) days from the date of mailing of the notice.

(b) A creditor failing to file his claim or to commence a judicial proceeding to contest the validity of a trust within the times provided is forever prohibited from making any claim against the assets of the settlor's trust or commencing any judicial proceeding against the settlor or the assets of the settlor's trust.