UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

For the fiscal year ended December 31, 2014

or

For the transition period from                      to                     

Commission file number                     

333-166711-02

(Commission File Number of issuing entity)

Citigroup Commercial Mortgage Trust 2012-GC8

(Exact name of issuing entity as specified in its charter)

333-166711

(Commission File Number of depositor)

Citigroup Commercial Mortgage Securities Inc.

(Exact name of depositor as specified in its charter)

Citigroup Global Markets Realty Corp.

Goldman Sachs Mortgage Company

Natixis Real Estate Capital LLC

(Exact name of sponsor as specified in its charter)

c/o Citibank, N.A.

388 Greenwich Street, 14^th Floor

New York, New York 10013

(Address of principal executive offices of issuing entity)

(212) 816-5614

Registrant’s telephone number, including area code

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

None

Securities registered pursuant to section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    ¨  Yes    x  No

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.    ¨  Yes    x  No

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    x  Yes    ¨  No

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).

Not Applicable

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§ 229.405 of this chapter) is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.

Not Applicable

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act).    ¨  Yes    x  No

State the aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of the registrant’s most recently completed second fiscal quarter.

Not Applicable

Indicate by check mark whether the registrant has filed all documents and reports required to be filed by Section 12, 13 or 15(d) of the Securities Exchange Act of 1934 subsequent to the distribution of securities under a plan confirmed by a court.

Not Applicable

Indicate the number of shares outstanding of each of the registrant’s classes of common stock, as of the latest practicable date.

Not Applicable

DOCUMENTS INCORPORATED BY REFERENCE

List hereunder the following documents if incorporated by reference and the Part of the Form 10-K (e.g., Part I, Part II, etc.) into which the document is incorporated: (1) Any annual report to security holders; (2) Any proxy or information statement; and (3) Any prospectus filed pursuant to Rule 424(b) or (c) under the Securities Act of 1933. The listed documents should be clearly described for identification purposes (e.g., annual report to security holders for fiscal year ended December 24, 1980).

See Item 15.

PART I

Omitted.

Omitted.

None.

Omitted.

Omitted.

Not applicable.

PART II

Omitted.

Omitted.

Omitted.

Omitted.

Omitted.

Omitted.

Omitted.

None.

PART III

Omitted.

Omitted.

Omitted.

Omitted.

Omitted.

ADDITIONAL DISCLOSURE ITEMS REQUIRED BY GENERAL INSTRUCTION J(2)

Item 1112(b) of Regulation AB

The property securing the Miami Center mortgage loan constitutes a significant obligor within the meaning of Item 1101(k)(2) of Regulation AB and as disclosed in the Prospectus Supplement for Citigroup Commercial Mortgage Trust 2012-GC8 filed on September 24, 2012. In accordance with Item 1112(b) of Regulation AB, the most recent unaudited net operating income of the significant obligor was $14,532,020 for the twelve month period ended December 31, 2014.

Item 1114(b)(2) and Item 1115(b) of Regulation AB

No entity or group of affiliated entities provides any external credit enhancement, uses any derivative instruments or other support for the certificates within this transaction.

Item 1117 of Regulation AB

Disclosure from Citibank, N.A., as Certificate Administrator:

Citibank, N.A. (“Citibank”) is acting as Certificate Administrator of this commercial mortgage-backed securities (“CMBS”) transaction. In the ordinary course of business, Citibank is involved in a number of legal proceedings, including in connection with its role as trustee of certain residential mortgage-backed securities (“RMBS”) transactions. One such proceeding was a civil action filed against Citibank in the Supreme Court of the State of New York on June 18, 2014 by a group of investors in 48 private-label RMBS trusts for which Citibank serves or did serve as trustee, asserting claims for alleged violations of the Trust Indenture Act of 1939, breach of contract, breach of fiduciary duty and negligence based on Citibank’s alleged failure to perform its duties as trustee for the 48 RMBS trusts. On November 24, 2014, plaintiffs sought leave to withdraw this action. On the same day, a smaller subset of similar plaintiff investors in 27 private-label RMBS trusts for which Citibank serves as trustee filed a new civil action against Citibank in the Southern District of New York asserting similar claims as the prior action filed in state court.

There can be no assurances as to the outcome of litigation or the possible impact of litigation on the trustee or the RMBS trusts. However, Citibank denies liability and intends to vigorously defend against the litigation. Furthermore, neither the above-disclosed litigation nor any other pending legal proceeding involving Citibank will materially affect Citibank’s ability to perform its duties as Certificate Administrator under the Pooling and Servicing Agreement for this CMBS transaction.

Disclosure from U.S. Bank National Association, as Trustee:

In June 2014, a civil complaint was filed in the Supreme Court of the State of New York, New York County, by a group of institutional investors against U.S. Bank National Association (“U.S. Bank”), in its capacity as trustee or successor trustee (as the case may be) under certain residential mortgage backed securities (“RMBS”) trusts. The plaintiffs are investment funds formed by nine investment advisors (AEGON, BlackRock, Brookfield, DZ Bank, Kore, PIMCO, Prudential, Sealink and TIAA) that purport to be bringing suit derivatively on behalf of 841 RMBS trusts that issued $771 billion in original principal amount of securities between 2004 and 2008. According to the plaintiffs, cumulative losses for these RMBS trusts equal $92.4 billion as of the date of the complaint. The complaint is one of six similar complaints filed against RMBS trustees (Deutsche Bank, Citibank, HSBC, Bank of New York Mellon and Wells Fargo) by certain of these plaintiffs. The complaint against U.S. Bank alleges the trustee caused losses to investors as a result of alleged failures by the sponsors, mortgage loan sellers and servicers for these RMBS trusts and asserts causes of action based upon the trustee’s purported failure to enforce repurchase obligations of mortgage loan sellers for alleged breaches of representations and warranties concerning loan quality. The complaint also asserts that the trustee failed to notify securityholders of purported events of default allegedly caused by breaches by mortgage loan servicers and that the trustee purportedly failed to abide by appropriate standards of care following events of default. Relief sought includes money damages in an unspecified amount and equitable relief. In November 2014, the plaintiffs sought leave to voluntarily dismiss their original state court complaint and filed a substantially similar complaint in the United States District Court for the Southern District of New York. The federal civil complaint added a class action allegation and a change in the total number of named trusts to 843 RMBS trusts. In December 2014, the plaintiffs’ motion to voluntarily dismiss their original state court complaint was granted. Other cases alleging similar causes of action have previously been filed against U.S. Bank and other trustees by RMBS investors in other transactions.

There can be no assurances as to the outcome of the litigation, or the possible impact of the litigation on the trustee or the RMBS trusts. However, U.S. Bank denies liability and believes that it has performed its obligations under the RMBS trusts in good faith, that its actions were not the cause of losses to investors and that it has meritorious defenses, and it intends to contest the plaintiffs’ claims vigorously.

Item 1119 of Regulation AB

Provided previously in the prospectus supplement of the Registrant relating to the issuing entity and filed pursuant to Rule 424 of the Securities Act of 1933, as amended.

Item 1122 of Regulation AB

The reports on assessment of compliance with servicing criteria for asset-backed securities and related attestation reports are attached hereto under Item 15.

Item 1123 of Regulation AB

The servicer compliance statements are attached hereto under Item 15.

PART IV

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: March 31, 2015

Citigroup Commercial Mortgage Securities Inc.

(Depositor)

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