Curbline Properties Corp. (the "Company") has entered into an ATM Equity Offering Sales Agreement, dated June 2, 2026 (the "Equity Sales Agreement"), with Jefferies LLC, BNY Mellon Capital Markets, LLC, BofA Securities, Inc., BTIG, LLC, Capital One Securities, Inc., Goldman Sachs & Co. LLC, KeyBanc Capital Markets Inc., Morgan Stanley & Co. LLC, Nomura Securities International, Inc., StoneX Financial Inc. and Wells Fargo Securities, LLC, as sales agents (except in the case of Nomura Securities International, Inc. and StoneX Financial Inc.), principals (except in the case of Nomura Securities International, Inc. and StoneX Financial Inc.) and/or Forward Sellers (as defined below) (except in the case of BTIG, LLC and Capital One Securities, Inc.) (in any such capacity, each, an "Agent," and, collectively, the "Agents") and the Forward Purchasers (as defined below), relating to shares of its common stock, $0.01 par value per share ("common stock"), offered by this prospectus supplement and the accompanying prospectus pursuant to a continuous offering program. In accordance with the terms of the Equity Sales Agreement, an aggregate gross sales price of up to $400 million of shares of our common stock may be offered and sold from time to time through the Agents, as our sales agents or, if applicable, as Forward Sellers (as defined below), or directly to the Agents, as principals.

In connection with the entry into the Equity Sales Agreement, the Company's "at-the-market" equity offering program pursuant to the Company's prior equity sales agreement, dated as of October 1, 2025 (the "Prior Equity Sales Agreement"), was terminated. As of its termination, shares of common stock having an aggregate offering price of approximately $7.1 million were not sold under the Prior Equity Sales Agreement. In addition, shares of common stock having an aggregate offering price of approximately $199.9 million are subject to outstanding forward sale agreements entered into pursuant to the Prior Equity Sales Agreement that will remain outstanding following its termination in accordance with the terms of such forward sale agreements.

There are certain restrictions on transfer and ownership of our common stock intended to, among other things, preserve our qualification as a real estate investment trust ("REIT") for federal income tax purposes. See "Description of Capital Stock—Restrictions on Ownership and Transfer" in the accompanying prospectus.