LEHMAN BROTHERS HOLDINGS INC., SELLER and STRUCTURED ASSET SECURITIES CORPORATION, PURCHASER MORTGAGE LOAN SALE AND ASSIGNMENT AGREEMENT Dated as of December 1, 2004 Structured Asset Securities Corporation (Mortgage Pass-Through Certificates, Series 2004-23XS)

EXECUTION

LEHMAN BROTHERS HOLDINGS INC.,

SELLER

and

STRUCTURED ASSET SECURITIES CORPORATION,

PURCHASER

MORTGAGE LOAN SALE AND ASSIGNMENT AGREEMENT

Dated as of December 1, 2004

Structured Asset Securities Corporation

(Mortgage Pass-Through Certificates, Series 2004-23XS)

TABLE OF CONTENTS

Page

ARTICLE I. CONVEYANCE OF MORTGAGE LOANS    3

Section 1.01.

Sale of Mortgage Loans.

3

Section 1.02.

Delivery of Documents.

4

Section 1.03.

Review of Documentation.

4

Section 1.04.

Representations and Warranties of the Seller.

4

Section 1.05.

Grant Clause.

14

Section 1.06.

Assignment by Depositor.

14

ARTICLE II. MISCELLANEOUS PROVISIONS    14

Section 2.01.

Binding Nature of Agreement; Assignment.

14

Section 2.02.

Entire Agreement.

14

Section 2.03.

Amendment.

14

Section 2.04.

Governing Law.

15

Section 2.05.

Severability of Provisions.

15

Section 2.06.

Indulgences; No Waivers.

16

Section 2.07.

Headings Not to Affect Interpretation.

16

Section 2.08.

Benefits of Agreement.

16

Section 2.09.

Counterparts.

16

SCHEDULE A

Transferred Mortgage Loan Schedule (including Prepayment Charge

Schedule)

SCHEDULE B

Bank Originated Mortgage Loan Schedule (including Prepayment Charge Schedule)

EXHIBIT A

Certain Defined Terms

EXHIBIT B

Form of Terms Letter

This MORTGAGE LOAN SALE AND ASSIGNMENT AGREEMENT, dated as of December 1, 2004 (the “Agreement”), is executed by and between Lehman Brothers Holdings Inc. (“Holdings” or the “Seller”) and Structured Asset Securities Corporation (the “Depositor”).

All capitalized terms not defined herein or in Exhibit A attached hereto shall have the same meanings assigned to such terms in that certain trust agreement (the “Trust Agreement”) dated as of December 1, 2004, among the Depositor, Aurora Loan Services Inc., as master servicer (the “Master Servicer”), and Citibank, N.A., as trustee (the “Trustee”).

W I T N E S S E T H :

WHEREAS, Lehman Brothers Bank, FSB (the “Bank”), pursuant to the following specified mortgage loan purchase and warranties agreements (each a “Bank Transfer Agreement,” and collectively, the “Transfer Agreements”), has purchased or received from certain transferors identified below (each a “Transferor,” and collectively, the “Transferors”) certain mortgage loans, each identified on the Mortgage Loan Schedule attached hereto as Schedule A (the “Transferred Mortgage Loans”):

1.

Loan Purchase Agreement by and between the Bank and E-Loan Mortgage dated as of December 5, 2002;

2.

Master Mortgage Loan Purchase and Warranties Agreement by and between the Bank and First National Bank of Nevada dated as of August 27, 2004;

3.

Flow Purchase and Warranties Agreement by and between the Bank and IndyMac Bank, FSB dated as of February 13, 2001.  Amendment dated as of June 27, 2001, July 19, 2002 and December 1, 2003;

4.

Flow Mortgage Loan Purchase and Warranties Agreement by and between the Bank and Nation One Mortgage Company Inc. dated as of March 29, 2004;

5.

Flow Mortgage Loan Purchase and Warranties Agreement by and between Bay Capital Corporation and the Bank dated as of September 20, 2004;

6.

Flow Mortgage Loan Purchase and Warranties Agreement by and between the Bank and Mortgage IT, Inc. dated as of January 6, 2004;

7.

Flow Mortgage Loan Purchase and Warranties Agreement by and between the Bank, National Bank of Commerce, Central California Bank & Trust, NBC Bank, FSB, First Market Bank and Commerce Finance Company dated as of August 1, 2001;

8.

Flow Mortgage Loan Purchase and Warranties Agreement by and between the Bank and Oak Street Mortgage LLC dated as of April 1, 2003;

9.

Flow Mortgage Loan Purchase and Warranties Agreement dated as of October 20, 2004 by and between the Bank and Paul Financial, LLC; and

10.

Purchase Agreement represented by Buyid “Provident Bank- JUN00.”

WHEREAS, in addition to the Transferred Mortgage Loans, the Bank has directly underwritten and funded certain mortgage loans originated by Aurora Loan Services Inc.,  correspondents and others identified on the Mortgage Loan Schedule attached hereto as Schedule B (the “Bank Originated Mortgage Loans” and together with the Transferred Mortgage Loans, the “Mortgage Loans”);

WHEREAS, pursuant to an assignment and assumption agreement (the “Assignment and Assumption Agreement”), dated as of December 1, 2004, between the Bank, as assignor, and the Seller, as assignee, the Bank has assigned all of its right, title and interest in and to the foregoing Bank Transfer Agreements and related Bank Mortgage Loans as listed on Schedule A, in the case of Transferred Mortgage Loans, or Schedule B, in the case of the Bank Originated Mortgage Loans, and the Seller has accepted the rights and benefits of, and assumed the obligations of the Bank under, the Bank Transfer Agreements;

WHEREAS, the Seller is a party to the following servicing agreements (together, the “Servicing Agreements”) pursuant to which the Mortgage Loans are to be initially serviced by certain servicers as indicated below (each, a “Servicer” and, collectively, the “Servicers”):

1.

Servicing Agreement, dated as of December 1, 2004, among the Seller, as seller, and Aurora Loan Services Inc. (“Aurora”) in the dual capacities of servicer and master servicer;

2.

Transfer Notice dated December 30, 2004, from Holdings, as owner, and Colonial Savings, F.A. (“Colonial”), as servicer, in connection with the Correspondent Servicing Agreement dated as of June 26, 2002, by and among Colonial, the Bank and the Master Servicer; and

3.

Servicing Agreement dated as of December 1, 2004, among the Seller, as seller and Midwest Loan Services, Inc., as servicer.

WHEREAS, the Seller desires to sell, without recourse, all of its rights, title and interest in and to the Mortgage Loans to the Depositor, assign all of its rights and interest under each Transfer Agreement and each Servicing Agreement relating to the Mortgage Loans referred to above, other than any servicing rights retained by the Seller hereunder, and delegate all of its obligations thereunder, to the Depositor; and

WHEREAS, the Seller and the Depositor acknowledge and agree that the Depositor will convey the Mortgage Loans to a Trust Fund created pursuant to the Trust Agreement, assign all of its rights and delegate all of its obligations hereunder to the Trustee for the benefit of the Certificateholders, and that each reference herein to the Depositor is intended, unless otherwise specified, to mean the Depositor or the Trustee, as assignee, whichever is the owner of the Mortgage Loans from time to time.

NOW, THEREFORE, in consideration of the mutual agreements herein set forth, and for other good and valuable consideration, the receipt and adequacy of which are hereby acknowledged, the Seller and the Depositor agree as follows:

ARTICLE I.

CONVEYANCE OF MORTGAGE LOANS

Section 1.01.

Sale of Mortgage Loans .

(a)

Sale of Mortgage Loans .  Concurrently with the execution and delivery of this Agreement, the Seller does hereby transfer, assign, set over, deposit with and otherwise convey to the Depositor, without recourse, subject to Sections 1.03 and 1.04, all the right, title and interest of the Seller in and to the Mortgage Loans identified on Schedules A and B hereto, having an approximate aggregate principal balance of $455,762,525.  Such conveyance includes, without limitation, the right to all distributions of principal and interest received on or with respect to the Mortgage Loans on and after the Cut-off Date, other than payments of principal and interest due on or before such date, and all such payments due after such date but received prior to such date and intended by the related Mortgagors to be applied after such date, all Prepayment Charges received on or with respect to the Mortgage Loans on or after the Cut-off Date, together with all of the Seller’s right, title and interest in and to each related account and all amounts from time to time credited to and the proceeds of such account, any REO Property and the proceeds thereof, the Seller’s rights under any Insurance Policies relating to the Mortgage Loans, the Seller’s security interest in any collateral pledged to secure the Mortgage Loans, including the Mortgaged Properties, and any proceeds of the foregoing.

Concurrently with the execution and delivery of this Agreement, the Seller hereby assigns to the Depositor all of its rights and interest under each Transfer Agreement and each Servicing Agreement, other than any servicing rights retained thereunder, and delegates to the Depositor all of its obligations thereunder, to the extent relating to the Mortgage Loans.  The Seller and the Depositor further agree that this Agreement incorporates the terms and conditions of any assignment and assumption agreement or other assignment document required to be entered into under any of the Transfer Agreements (any such document an “Assignment Agreement”) and that this Agreement constitutes an Assignment Agreement under such Transfer Agreement, and the Depositor hereby assumes the obligations of the assignee under each such Assignment Agreement.  Concurrently with the execution hereof, the Depositor tenders the purchase price set forth in that certain Terms Letter dated as of the date hereof, the form of which is attached as Exhibit B hereto (the “Purchase Price”).  The Depositor hereby accepts such assignment and delegation, and shall be entitled to exercise all the rights of the Seller under each Transfer Agreement and each Servicing Agreement, other than any servicing rights thereunder, as if the Depositor had been a party to each such agreement.

(b)

Schedules of Mortgage Loans .  The Depositor and the Seller have agreed upon which of the Mortgage Loans owned by the Seller are to be purchased by the Depositor pursuant to this Agreement and the Seller will prepare on or prior to the Closing Date a final schedule describing such Mortgage Loans (the “Mortgage Loan Schedule”).  The Mortgage Loan Schedule shall conform to the requirements of the Depositor as set forth in this Agreement and to the definition of “Mortgage Loan Schedule” under the Trust Agreement.  The Mortgage Loan Schedule attached hereto as Schedule A specifies those Mortgage Loans that are Transferred Mortgage Loans and the Mortgage Loan Schedule attached hereto as Schedule B specifies those Mortgage Loans that are Bank Originated Loans each of which categories of Mortgage Loans have been assigned by the Bank to the Seller pursuant to the Assignment and Assumption Agreement.

Section 1.02.

Delivery of Documents .  (a)

In connection with such transfer and assignment of the Mortgage Loans hereunder, the Seller shall, at least three (3) Business Days prior to the Closing Date, deliver, or cause to be delivered, to the Depositor (or its designee) the documents or instruments with respect to each Mortgage Loan (each a “Mortgage File”) so transferred and assigned, as specified in the related Transfer Agreements or Servicing Agreements.

(b)

For Mortgage Loans (if any) that have been prepaid in full on or after the Cut-off Date and prior to the Closing Date, the Seller, in lieu of delivering the related Mortgage Files, herewith delivers to the Depositor an Officer’s Certificate which shall include a statement to the effect that all amounts received in connection with such prepayment that are required to be deposited in the Collection Account maintained by the Master Servicer for such purpose have been so deposited.

Section 1.03.

Review of Documentation .

The Depositor, by execution and delivery hereof, acknowledges receipt of the Mortgage Files pertaining to the Mortgage Loans listed on the Mortgage Loan Schedule, subject to review thereof by LaSalle Bank National Association and U.S. Bank National Association, as applicable (each, a “Custodian” and, collectively, the “Custodians”), for the Depositor.  Each Custodian is required to review, within 45 days following the Closing Date, each applicable Mortgage File.  If in the course of such review the related Custodian identifies any Material Defect, the Seller shall be obligated to cure such Material Defect or to repurchase the related Mortgage Loan from the Depositor (or, at the direction of and on behalf of the Depositor, from the Trust Fund), or to substitute a Qualifying Substitute Mortgage Loan therefor, in each case to the same extent and in the same manner as the Depositor is obligated to the Trustee and the Trust Fund under Section 2.02(c) of the Trust Agreement.

Section 1.04.

Representations and Warranties of the Seller .

(a)

The Seller hereby represents and warrants to the Depositor that as of the Closing Date:

(i)

the Seller is a corporation duly organized, validly existing and in good standing under the laws governing its creation and existence and has full corporate power and authority to own its property, carry on its business as presently conducted and enter into and perform its obligations under the Assignment and Assumption Agreement and this Agreement;

(ii)

the execution and delivery by the Seller of the Assignment and Assumption Agreement and this Agreement have been duly authorized by all necessary corporate action on the part of the Seller; neither the execution and delivery of the Assignment and Assumption Agreement or this Agreement, nor the consummation of the transactions therein or herein contemplated, nor compliance with the provisions thereof or hereof, will conflict with or result in a breach of, or constitute a default under, any of the provisions of any law, governmental rule, regulation, judgment, decree or order binding on the Seller or its properties or the certificate of incorporation or bylaws of the Seller;

(iii)

the execution, delivery and performance by the Seller of the Assignment and Assumption Agreement and this Agreement and the consummation of the transactions contemplated thereby and hereby do not require the consent or approval of, the giving of notice to, the registration with, or the taking of any other action in respect of, any state, federal or other governmental authority or agency, except such as has been obtained, given, effected or taken prior to the date hereof;

(iv)

each of the Assignment and Assumption Agreement and this Agreement has been duly executed and delivered by the Seller and, assuming due authorization, execution and delivery by the Bank, in the case of the Assignment and Assumption Agreement, and the Depositor, in the case of this Agreement, constitutes a valid and binding obligation of the Seller enforceable against it in accordance with its respective terms, except as such enforceability may be subject to (A) applicable bankruptcy and insolvency laws and other similar laws affecting the enforcement of the rights of creditors generally and (B) general principles of equity regardless of whether such enforcement is considered in a proceeding in equity or at law; and

(v)

there are no actions, suits or proceedings pending or, to the knowledge of the Seller, threatened or likely to be asserted against or affecting the Seller, before or by any court, administrative agency, arbitrator or governmental body (A) with respect to any of the transactions contemplated by the Assignment and Assumption Agreement or this Agreement or (B) with respect to any other matter which in the judgment of the Seller will be determined adversely to the Seller and will if determined adversely to the Seller materially and adversely affect it or its business, assets, operations or condition, financial or otherwise, or adversely affect its ability to perform its obligations under the Assignment and Assumption Agreement or this Agreement.

(b)

The representations and warranties of each Transferor with respect to the Mortgage Loans in the applicable Transfer Agreement were made as of the date of such Transfer Agreement.  To the extent that any fact, condition or event with respect to a Transferred Mortgage Loan constitutes a breach of both (i) a representation or warranty of a Transferor under the applicable Transfer Agreement and (ii) a representation or warranty of the Seller under this Agreement, the sole right or remedy of the Depositor with respect to a breach by the Seller of such representation and warranty (other than a breach by the Seller of the representations made by it pursuant to Sections 1.04(b)(xii), (xiii), (xiv) and (xv), shall be the right to enforce the obligations of such Transferor under any applicable representation or warranty made by it.  The representations made by the Seller pursuant to Sections 1.04(b)(xii), (xiii), (xiv) and (xv) shall be direct obligations of the Seller.  The Depositor acknowledges and agrees that the representations and warranties of the Seller in this Section 1.04(b) (other than any representations and warranties made pursuant to Sections 1.04(b)(xii), (xiii), (xiv) and (xv) by it) are applicable only to facts, conditions or events that do not constitute a breach of any representation or warranty made by the related Transferor in the applicable Transfer Agreement.  The Seller shall have no obligation or liability with respect to any breach of a representation or warranty made by it with respect to the Transferred Mortgage Loans (other than any representations and warranties made by it pursuant to Sections 1.04(b)(xii), (xiii), (xiv) and (xv)) if the fact, condition or event constituting such breach also constitutes a breach of a representation or warranty made by the related Transferor in such Transfer Agreement, without regard to whether the related Transferor fulfills its contractual obligations in respect of such representation or warranty; provided, however, that if the related Transferor fulfills its obligations under the provisions of such Transfer Agreement by substituting for the affected Mortgage Loan a mortgage loan which is not a Qualifying Substitute Mortgage Loan, the Seller shall, in exchange for such substitute mortgage loan, provide the Depositor (a) with the applicable Purchase Price for the affected Mortgage Loan or (b) within the two-year period following the Closing Date, with a Qualified Substitute Mortgage Loan for such affected Mortgage Loan.  Subject to the foregoing, the Seller represents and warrants upon delivery of the Transferred Mortgage Loans to the Depositor hereunder, as to each that, as of the Closing Date:

(i)

The information set forth with respect to the Transferred Mortgage Loans on the Mortgage Loan Schedule provides an accurate listing of the Transferred Mortgage Loans, and the information with respect to each Transferred Mortgage Loan on the Mortgage Loan Schedule is true and correct in all material respects at the date or dates respecting which such information is given;

(ii)

There are no defaults (other than delinquency in payment) in complying with the terms of any Mortgage, and the Seller has no notice as to any taxes, governmental assessments, insurance premiums, water, sewer and municipal charges, leasehold payments or ground rents which previously became due and owing but which have not been paid;

(iii)

Except in the case of Cooperative Loans, if any, each Mortgage requires all buildings or other improvements on the related Mortgaged Property to be insured by a generally acceptable insurer against loss by fire, hazards of extended coverage and such other hazards as are customary in the area where the related Mortgaged Property is located pursuant to insurance policies conforming to the requirements of the guidelines of Fannie Mae or Freddie Mac.  If upon origination of the Transferred Mortgage Loan, the Mortgaged Property was in an area identified in the Federal Register by the Federal Emergency Management Agency as having special flood hazards (and such flood insurance has been made available), a flood insurance policy meeting the requirements of the current guidelines of the Federal Flood Insurance Administration is in effect, which policy conforms to the requirements of the current guidelines of the Federal Flood Insurance Administration.  Each Mortgage obligates the related Mortgagor thereunder to maintain the hazard insurance policy at the Mortgagor’s cost and expense, and on the Mortgagor’s failure to do so, authorizes the holder of the Mortgage to obtain and maintain such insurance at such Mortgagor’s cost and expense, and to seek reimbursement therefor from the Mortgagor.  Where required by state law or regulation, each Mortgagor has been given an opportunity to choose the carrier of the required hazard insurance, provided the policy is not a “master” or “blanket” hazard insurance policy covering the common facilities of a planned unit development.  The hazard insurance policy is the valid and binding obligation of the insurer, is in full force and effect, and will be in full force and effect and inure to the benefit of the Depositor upon the consummation of the transactions contemplated by this Agreement;

(iv)

Each Mortgage has not been satisfied, cancelled, subordinated or rescinded, in whole or in part, and the Mortgaged Property has not been released from the lien of the Mortgage, in whole or in part, nor has any instrument been executed that would effect any such release, cancellation, subordination or rescission;

(v)

The related Mortgage evidences a valid, subsisting, enforceable and perfected first lien on the related Mortgaged Property (including all improvements on the Mortgaged Property).  The lien of the Mortgage is subject only to: (1) liens of current real property taxes and assessments not yet due and payable and, if the related Mortgaged Property is a condominium unit, any lien for co