DBRS Rates Credit Suisse First Boston Mortgage Securities Corp., CSMC Series 2009-3R

DBRS has today assigned the following ratings to the Credit Suisse First Boston Mortgage Securities Corp., CSMC Series 2009-3R Certificates issued by CSMC Series 2009-3R (the Trust).

-- $15.0 million Class 18-A-3 rated at AAA
-- $50 Class 18-R rated at AAA
-- $25.0 million Class 19-A-3 rated at AAA
-- $50 Class 19-R rated at AAA
-- $80.2 million Class 25-A-1* rated at AAA
-- $53.5 million Class 25-A-3** rated at AAA
-- $13.4 million Class 25-A-4** rated at AAA
-- $13.4 million Class 25-A-5** rated at AAA
-- $66.8 million Class 25-A-8* rated at AAA
-- $50 Class 25-R rated at AAA
-- $30.4 million Class 28-A-1* rated at AAA
-- $19.4 million Class 28-A-3** rated at AAA
-- $5.5 million Class 28-A-4** rated at AAA
-- $5.5 million Class 28-A-5** rated at AAA
-- $24.9 million Class 28-A-8* rated at AAA
-- $50 Class 28-R rated at AAA
-- $3.8 million Class 29-A-1* rated at AAA
-- $3.1 million Class 29-A-3** rated at AAA
-- $762,000 Class 29-A-4** rated at AAA
-- $50 Class 29-R rated at AAA
-- $77.7 million Class 30-A-1* rated at AAA
-- $51.8 million Class 30-A-3** rated at AAA
-- $12.9 million Class 30-A-4** rated at AAA
-- $12.9 million Class 30-A-5** rated at AAA
-- $64.7 million Class 30-A-8* rated at AAA
-- $50 Class 30-R rated at AAA

DBRS rates a total of 6 groups (Group 18, 19, 25, 28, 29 and 30) in this resecuritization trust, each consisting of one seasoned senior residential mortgage-backed security (RMBS). Within each DBRS-rated group, the AAA ratings reflect the credit enhancement provided by subordination. The ratings also reflect the quality of the underlying securities. Certain classes of certificates (Exchangeable REMIC Certificates) are exchangeable for certain other classes of certificates (Exchangeable Certificates) and vice versa, in the combinations described in Annex II of the private placement memorandum.

Other than the specified classes above, DBRS does not rate any other certificates in these 6 groups or any certificates in Groups 1 through 17, 20 through 24, 26 and 27.

Interest and principal payments on the certificates will be made generally on the 27th day of each month commencing in June 2009. Within all DBRS-rated groups other than Group 29, interest payments will be distributed on a pro rata basis to the certificates, and principal will be distributed on a sequential basis to the certificates, in the order of priority specified in the private placement memorandum, until the certificate principal balances thereof are reduced to zero.

Within Group 29, interest payments will be distributed on a sequential basis to the certificates, provided that interest payments to Class 29-A-4 will be distributed as principal to Class 29-A-3, and interest payments to Class 29-A-2 will be distributed as principal on a sequential basis to Class 29-A-3 until the certificate principal balance has been reduced to zero, then to Class 29-A-4. Principal payments will be distributed on a sequential basis to the certificates until the certificate principal balance has been reduced to zero.

Any losses realized from the underlying securities within each group will be allocated in a reverse numerical order to the certificates.

The Trust is a resecuritization consisting of 30 senior RMBS, represented by various real estate mortgage investment conduits (REMICs). The REMICs are backed by pools of first-lien one- to four-family residential mortgages.

Notes:

• Denotes Exchangeable Certificate.
  ** Denotes Exchangeable REMIC Certificate.

All figures are in U.S. dollars unless otherwise noted.