MORTGAGE LOAN SALE AND ASSIGNMENT AGREEMENT

LEHMAN BROTHERS HOLDINGS INC.,

SELLER

and

STRUCTURED ASSET SECURITIES CORPORATION,

DEPOSITOR

MORTGAGE LOAN SALE AND ASSIGNMENT AGREEMENT

Dated as of November 1, 2006

Lehman XS Trust

(Mortgage Pass-Through Certificates, Series 2006-18N)

SCHEDULES  

This MORTGAGE LOAN SALE AND ASSIGNMENT AGREEMENT, dated as of November 1, 2006 (the "Agreement"), is executed by and between Lehman Brothers Holdings Inc. (the "Seller") and Structured Asset Securities Corporation (the "Depositor").

All capitalized terms not defined herein shall have the same meanings assigned to such terms in that certain Trust Agreement (the "Trust Agreement"), dated as of November 1, 2006, among the Depositor, Aurora Loan Services LLC, as master servicer ("Aurora"), and U.S. Bank National Association, as trustee (the "Trustee").

WITNESSETH :

WHEREAS, Lehman Brothers Bank, FSB (the "Bank"), pursuant to (i) the Flow Seller's Warranties and Servicing Agreement, dated as of June 1, 2004, by and between the Bank and Countrywide Home Loans, Inc. ("Countrywide"), as amended by the Amendment Reg AB dated as of January 31, 2006, and (ii) the Flow Subservicing Agreement, dated as of January 1, 2005, by and between GMAC Mortgage Corporation and the Bank, as amended by the Amendment Reg AB dated as of April 7, 2006 (each, a "Bank Transfer Agreement," has purchased or received certain mortgage loans identified on the Mortgage Loan Schedule attached hereto as Schedule A-1A (the "Bank Transferred Mortgage Loans"):

WHEREAS, Lehman Capital, a division of Lehman Brothers Holdings Inc. ("Lehman Capital"), pursuant to the following specified agreements (each an "LBH Agreement" and together with the Bank Transfer Agreement the "Transfer Agreements"), has purchased or received certain mortgage loans identified on the Mortgage Loan Schedule attached hereto as Schedule A-1B (the "LBH Mortgage Loans" and together with the Bank Transferred Mortgage Loans, the "Transferred Mortgage Loans"):

WHEREAS, in addition to the Bank Transferred Mortgage Loans, the Bank may have funded certain mortgage loans originated by Aurora Loan Services LLC identified on the Mortgage Loan Schedule attached hereto as Schedule A-2 (the "Bank Originated Mortgage Loans" and together with the Transferred Mortgage Loans, the "Mortgage Loans");

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WHEREAS, pursuant to an Assignment and Assumption Agreement (the "Assignment and Assumption Agreement"), dated as of November 1, 2006, 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 Bank Transfer Agreements, the Bank Transferred Mortgage Loans and any 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 (the "Servicing Agreements" and each a "Servicing Agreement") pursuant to which the Mortgage Loans are serviced by Countrywide Home Loans Servicing LP ("Countrywide Servicing"), IndyMac, RFC LLC and GMAC Mortgage, LLC ("GMAC") (each a "Servicer" and collectively the "Servicers"):

WHEREAS, the Seller desires to sell, without recourse, all of its rights, title and interest in and to the Mortgage Loans (exclusive of any Retained Interest on such Mortgage Loans) to the Depositor and to assign all of its rights and interest under the Transfer Agreements and the Servicing Agreements relating to the Mortgage Loans, and to 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.   Mortgage Loans .

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(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 (exclusive of any Retained Interest on such Mortgage Loans, if any) identified on Schedule A-1A, Schedule A-1B and Schedule A-2 hereto, having an aggregate principal balance as of the Cut-off Date of $1,027,393,147. Such conveyance includes, without limitation, the right to all distributions of principal and interest received on or with respect to the Mortgage Loans on or after November 1, 2006 other than (i) any amounts representing Retained Interest, if any, and (ii) 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, 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.

(b)   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 the Servicing Agreements except for (A) any rights against the Transferor with respect to (i) first payment date defaults or early payment date defaults or (ii) reimbursement of any amount in excess of the Purchase Price for a breach of a representation or warranty and (B) any right to receive Retained Interest if any, and 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 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 of $1,027,393,147. 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.

(c)   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-1A specifies those Mortgage Loans that are Bank Transferred Mortgage Loans, the Mortgage Loan Schedule attached hereto as Schedule A-1B specifies those Mortgage Loans that are LBH Mortgage Loans and the Mortgage Loan Schedule attached hereto as Schedule A-2 specifies those Mortgage Loans that are Bank Originated Mortgage Loans. The Bank Transferred Mortgage Loans and Bank Originated Mortgage Loans have been assigned by the Bank to the Seller pursuant to the Assignment and Assumption Agreement.

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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 the custodian, Deutsche Bank National Trust Company, U.S. Bank National Association or Wells Fargo Bank, N.A. (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, to carry on its business as presently conducted, and to enter into and perform its obligations under this Agreement and the Assignment and Assumption Agreement;

(ii)   The execution and delivery by the Seller of this Agreement and the Assignment and Assumption Agreement have been duly authorized by all necessary corporate action on the part of the Seller; neither the execution and delivery of this Agreement or the Assignment and Assumption Agreement, nor the consummation of the transactions herein or therein contemplated, nor compliance with the provisions hereof or thereof, 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;

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(iii)   The execution, delivery and performance by the Seller of this Agreement and the Assignment and Assumption Agreement and the consummation of the transactions contemplated hereby and thereby 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 this Agreement and the Assignment and Assumption 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 this Agreement or the Assignment and Assumption 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 this Agreement or the Assignment and Assumption Agreement.

(b)   The representations and warranties of each Transferor with respect to the Transferred 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 and warranties made pursuant to Sections 1.04(b)(xii), 1.04(b)(xvii), 1.04(b)(xviii), 1.04(b)(xix) and 1.04(b)(xx)) 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), 1.04(b)(xvii), 1.04(b)(xviii), 1.04(b)(xix) and 1.04(b)(xx) 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 the representations and warranties made pursuant to Sections 1.04(b)(xii), 1.04(b)(xvii), 1.04(b)(xviii), 1.04(b)(xix) and 1.04(b)(xx)) 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 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 Transferred Mortgage Loan. Subject to the foregoing, the Seller represents and warrants upon delivery of the Transferred Mortgage Loans to the Depositor hereunder on the Closing Date, as to each, that:

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(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 FNMA or FHLMC. If upon origination of a 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