{"url_path":"/sec/cik-0002128774/8-k/2026-06-25/body","section_key":"body","section_title":"Body","topic":"sec","document":{"doc_type":"8-K","doc_date":"2026-06-25","source_url":"https://www.sec.gov/Archives/edgar/data/2128774/0001539497-26-001868-index.html","accession_number":"0001539497-26-001868","cik":"0002128774","ticker":null,"issuer_name":"BMO 2026-5C15 Mortgage Trust","edgar_url":"https://www.sec.gov/Archives/edgar/data/2128774/0001539497-26-001868-index.html","primary_entity_key":"0002128774","primary_entity_name":"BMO 2026-5C15 Mortgage Trust"},"word_count":1393,"has_tables":true,"body_markdown":"EX-5\n2\nexh_5-opinion.htm\nLEGALITY OPINION OF ORRICK, HERRINGTON & SUTCLIFFE LLP, DATED JUNE 25, 2026\n\n**Exhibit 5**\n\n****\n\nJune 25, 2026\n\n**Orrick,\nHerrington & Sutcliffe LLP**\n\n51\nWest 52nd\nStreet\n\nNew\nYork, NY 10019-6142\n\n**+1 212 506 5000\n\nBMO Commercial Mortgage Securities\nLLC\n\n \n\n**orrick.com**\n\nc/o BMO Capital Markets Corp.\n\n151 West 42nd Street\n\nNew York, New York 10036\n\nRe:BMO 2026-5C15 Mortgage Trust,\n\nCommercial Mortgage Pass-Through Certificates, Series 2026-5C15\n\nLadies and Gentlemen:\n\nWe have acted as special\ncounsel to BMO Commercial Mortgage Securities LLC (the “Depositor”) in connection with the transactions contemplated\nby the following agreements (collectively, the “Agreements”): (i) that certain Pooling and Servicing Agreement, dated\nas of June 1, 2026 (the “Pooling and Servicing Agreement”), between the Depositor, Midland Loan Services, a Division\nof PNC Bank, National Association, as master servicer, 3650 REIT Loan Servicing LLC, as special servicer, BellOak, LLC, as operating advisor\nand asset representations reviewer, and Computershare Trust Company, National Association, as certificate administrator and trustee, pursuant\nto which the BMO 2026-5C15 Mortgage Trust, Commercial Mortgage Pass-Through Certificates, Series 2026-5C15, Class A-1, Class A-2,\nClass A-3, Class X-A, Class X-B, Class A-S, Class B and Class C (the “Certificates”), are being issued\non the date hereof; and (ii) that certain Underwriting Agreement, dated as of June 12, 2026 (the “Underwriting Agreement”),\nbetween the Depositor, BMO Capital Markets Corp. (“BMO Capital”), Goldman Sachs & Co. LLC (“GS&Co.”),\nSG Americas Securities, LLC (“SGAS”), UBS Securities LLC (“UBS Securities”), Wells Fargo Securities,\nLLC (“Wells Fargo Securities”), Academy Securities, Inc. (“Academy”), Bancroft Capital, LLC (“Bancroft”),\nBlaylock Van, LLC (“Blaylock Van”) and Drexel Hamilton, LLC (“Drexel”; and BMO Capital, GS&Co.,\nSGAS, UBS Securities, Wells Fargo Securities, Academy, Bancroft, Blaylock Van and Drexel, collectively, the “Underwriters”),\npursuant to which the Underwriters have agreed to purchase, subject to the satisfaction of the conditions set forth therein, the Certificates.\nCapitalized terms used but not defined in this letter have the respective meanings assigned to such terms in the Pooling and Servicing\nAgreement.\n\nThe Certificates have been\noffered pursuant to the Depositor’s prospectus, dated June 12, 2026 (including the annexes and exhibits attached thereto, but excluding\nany electronic media that may accompany the printed version thereof, the “Prospectus”).\n\nIn rendering the opinions\nset forth below, we have examined and relied upon originals, copies or specimens, certified or otherwise identified to our satisfaction,\nof the Agreements and such certificates, entity and public records, agreements and instruments and other documents,\n\nBMO 2026-5C15 Mortgage Trust\n\nJune 25, 2026\n\nPage 2\n\n \n\nincluding, among other things, the documents\ndelivered on the date hereof, as we have deemed appropriate as a basis for the opinions expressed below. Furthermore, except for the matters\nthat are specifically addressed in any opinion expressed below, we have assumed, to the extent relevant to the opinions expressed below,\n(i) the authenticity of all documents submitted to us as originals or as copies or specimens thereof, the conformity to the originals\nof all documents submitted to us as copies or specimens, the genuineness of all signatures and the legal capacity of natural persons,\n(ii) the necessary entity formation and continuing existence in the jurisdiction of formation, and the necessary licensing and qualification\nin all jurisdictions, of all parties to all documents, (iii) the enforceability (as limited by bankruptcy and other insolvency laws) and,\nwith respect thereto and to any other matter herein to which relevant, any necessary entity power and authority, authorization, execution,\nauthentication, payment and delivery of, under and with respect to all documents to which this opinion letter relates, (iv) that the execution,\ndelivery and performance of the documents to which this opinion relates do not contravene the organizational documents of any party, (v)\nthe necessary ownership of and/or other rights and interests in assets, and the necessary adequacy and fairness of any consideration for\nsuch assets, (vi) the accuracy of the representations and warranties as to factual matters, and compliance by the parties thereto with\nthe covenants, contained in any document referred to herein or otherwise reviewed by us in connection with rendering this opinion letter,\n(vii) the conformity of the underlying assets and related documents to the requirements of any agreement to which this opinion letter\nrelates and (viii) that there is not any other agreement that modifies or supplements the agreements expressed in any document to which\nthis opinion letter relates in a manner that affects the correctness of any opinion expressed below. Except as expressly set forth herein,\nwe have not undertaken any independent investigation (including, without limitation, conducting any review, search or investigation of\nany public files, records or dockets) to determine the existence or absence of the facts that are material to our opinions, and no inference\nas to our knowledge concerning such facts should be drawn from our reliance on the representations of the Depositor and others in connection\nwith the preparation and delivery of this opinion letter.\n\nIn addition, we assume,\nfor purposes of this opinion letter, the conformity of the text of the Prospectus filed with the Securities and Exchange Commission (the\n“Commission”) through the Commission’s Electronic Data Gathering, Analysis and Retrieval System to the printed\ncopies of such document reviewed by us.\n\nIn rendering this opinion\nletter, we do not express any opinion concerning any law other than the laws of the State of New York and the federal laws of the United\nStates of America. In addition, we do not express any opinion herein with respect to any matter not specifically addressed in the opinions\nexpressed below.\n\nBased upon and subject\nto the foregoing, it is our opinion that:\n\n1.\nWhen the Certificates have been duly executed, authenticated or countersigned (as applicable) and delivered by the Certificate\nAdministrator in the manner contemplated by the Pooling and Servicing Agreement, and paid for and sold to the Underwriters in accordance\nwith\n\nBMO 2026-5C15 Mortgage Trust\n\nJune 25, 2026\n\nPage 3\n\n \n\nthe Underwriting Agreement, the Certificates\nwill be validly issued and outstanding, fully paid and non-assessable and entitled to the benefits of the Pooling and Servicing Agreement.\n\n2. The\ndescriptions of federal income tax consequences appearing under the heading “MATERIAL FEDERAL INCOME TAX CONSEQUENCES” in\nthe Prospectus, while not purporting to discuss all possible federal income tax consequences of an investment in the Certificates, accurately\ndescribe in all material respects the federal income tax consequences to holders of the Certificates which are discussed, under existing\nlaw and subject to the qualifications and assumptions stated therein. We also hereby confirm and adopt the opinions expressly set forth\nunder such heading, under existing law and subject to the qualifications and assumptions stated therein.\n\nThis opinion letter is\nrendered for the sole benefit of the addressee hereof with respect to the matters specifically addressed herein, and no other person or\nentity is entitled to rely hereon. The procedures undertaken by us in connection with this opinion letter do not constitute “due\ndiligence services” as defined in Rule 17g-10 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”),\nand this opinion letter does not constitute a “due diligence report” for purposes of Rule 15Ga-2 of the Exchange Act. No person\nis permitted to use, furnish or refer to this opinion letter in connection with such rules without our prior written approval. We assume\nno obligation to revise, supplement or withdraw this opinion letter, or otherwise inform the addressee hereof or other person or entity,\nwith respect to any change occurring subsequent to the delivery hereof in any applicable fact or law or any judicial or administrative\ninterpretation thereof, even though such change may affect a legal analysis or conclusion contained herein.\n\nWe hereby consent to the\nfiling of this opinion letter as an exhibit to the Depositor’s Registration Statement on Form SF-3 (File No. 333-280224) (the “Registration\nStatement”), and to the use of our name in the Prospectus under the headings “LEGAL MATTERS” and “MATERIAL\nFEDERAL INCOME TAX CONSEQUENCES.” This consent is not to be construed as an admission that we are “persons” within the\nmeaning of Section 7(a) or 11(a)(4) of the Securities Act of 1933, as amended, or “experts” within the meaning of Section\n11 thereof, with respect to any portion of the Registration Statement.\n\nIn addition, we disclaim\nany obligation to update this letter for changes in fact or law, or otherwise.\n\nVery truly yours,\n\n/s/ Orrick Herrington & Sutcliffe LLP\n\nOrrick Herrington & Sutcliffe LLP"}