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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): May 13, 2026

Core Natural Resources, Inc.

(Exact name of registrant as specified in its charter)

Delaware

001-38147

82-1954058

(State or other jurisdiction of incorporation)

(Commission File Number)

(IRS Employer

Identification No.)

275 Technology Drive Suite 101

Canonsburg, Pennsylvania 15317

(Address of principal executive offices)

(Zip code)

Registrant's telephone number, including area code:

(724) 416-8300

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:


Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, $0.01 par value	CNR	New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.04 Mine Safety – Reporting of Shutdowns and Patterns of Violations.

On May 13, 2026, Wolf Run Mining LLC, a subsidiary of Core Natural Resources, Inc., received an imminent danger order under section 107(a) of the Federal Mine Safety and Health Act of 1977 at the Leer South mine located in Barbour County, West Virginia. The order stated that an inspector found elevated methane concentrations in an area of the mine. The Mine Safety and Health Administration (“MSHA”) terminated the 107(a) order early on May 14, 2026, and after further discussion between Leer South’s mine management and MSHA, on May 18, 2026, MSHA determined that an imminent danger had never existed and the order was vacated.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.


			Core Natural Resources, Inc.
			(Registrant)
			By:			/s/ MITESHKUMAR B. THAKKAR
						Miteshkumar B. Thakkar
						President and Chief Financial Officer

Dated: May 19, 2026