Core Natural Resources, Inc.

Our operations are subject to a variety of risks and disputes normally incidental to our business. As a result, we may, at any given time, be a defendant in various legal proceedings and litigation arising in the ordinary course of business. We are not currently subject to any material litigation other than those described in Note 14—Commitments and Contingent Liabilities in the Notes to the Condensed Consolidated Financial Statements in this Report, which descriptions are incorporated herein by this reference.

SEC regulations require us to disclose certain information about environmental proceedings if we reasonably believe that such proceedings may result in monetary sanctions above a stated threshold. We use a threshold of $1 million for purposes of determining whether disclosure of any such proceedings is required, as permitted pursuant to Item 103(c)(3)(iii) of Regulation S-K. Except as described below, no such environmental proceedings were pending or contemplated as of September 30, 2026.

On July 23, 2026, the Company received an inspection report from the Colorado Department of Public Health and Environment, Air Pollution Control Division (the “Division”), finding the Company’s West Elk mine out of compliance with volatile organic compound emission limits under its Title V operating permit and recommending that the Division initiate an enforcement case with respect to these findings. On August 20, 2026, the Division issued a compliance advisory formally notifying the Company of the alleged noncompliance. The Division has not indicated the amount of any monetary penalty or other enforcement remedy it may seek. The Company continues to engage in discussions with the Division.