ADTN · ADTRAN Holdings, Inc.

Represents a restricted stock award grant that vests in full on the first anniversary of the date of grant.

The reporting person transferred 10,469 shares of the Issuer's common stock to a donor-advised fund sponsored by a charitable organization under Section 501(c)(3) of the Internal Revenue Code.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $14.69 to $14.765, inclusive. The reporting person undertakes to provide to ADTRAN Holdings, Inc. (the Issuer), any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote (1) to this Form 4.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

The stock option vested and was fully exercisable.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

These shares were sold in a single transaction at $15.00 per share.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $15.00 to $15.69, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within this range.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

The stock option vested and was fully exercisable.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $14.355 to $15.69, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within this range.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

The transactions reported on this Form 4 were effectuated pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025.

The stock option vested and was fully exercisable.

Represents a grant of restricted stock units that vest in four equal and annual installments beginning on the first anniversary date of the grant.

Represents a grant of restricted stock units that vest in four equal and annual installments beginning on the first anniversary date of the grant.

Represents a grant of restricted stock units that vest in four equal and annual installments beginning on the first anniversary date of the grant.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $10.24 to $10.37, inclusive. The reporting person undertakes to provide to ADTRAN Holdings, Inc. (the Issuer), any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote (1) to this Form 4.

These shares represent the vesting of performance stock units that were awarded pursuant to a grant on January 20, 2023 under the Amended and Restated ADTRAN Holdings, Inc. 2020 Employee Stock Incentive Plan.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted performance stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted performance stock units.

On January 28, 2026, the Reporting Person filed a Form 4 which inadvertently understated the number of shares withheld for taxes in connection with the vesting event reported therein. This amendment is being filed to correct the number of shares withheld and the total number of shares directly held by the Reporting Person following such withholding.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Represents a restricted stock award grant that vests in full on the first anniversary of the date of grant.

Represents a restricted stock award grant that vests in full on the first anniversary of the date of grant.

Represents a restricted stock award grant that vests in full on the first anniversary of the date of grant.

Represents a restricted stock award grant that vests in full on the first anniversary of the date of grant.

Represents a restricted stock award grant that vests in full on the first anniversary of the date of grant.

Represents a restricted stock award grant that vests in full on the first anniversary of the date of grant.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $7.75 to $8.00, inclusive. The reporting person undertakes to provide to ADTRAN Holdings, Inc. (the Issuer), any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote (1) to this Form 4.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $7.32 to $7.33, inclusive. The reporting person undertakes to provide to ADTRAN Holdings, Inc. (the Issuer), any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote (1) to this Form 4.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Represents a grant of restricted stock units that vest in four equal and annual installments beginning on the first anniversary date of the grant.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted restricted stock units.

These shares represent the vesting of performance stock units that were awarded pursuant to a grant on May 24, 2023 under the Amended and Restated ADTRAN Holdings, Inc. 2020 Employee Stock Incentive Plan.

Represents a grant of restricted stock units that vest in four equal and annual installments beginning on the first anniversary date of the grant. Remarks:

Represents a grant of restricted stock units that vest in four equal and annual installments beginning on the first anniversary date of the grant. Remarks:

Represents a grant of restricted stock units that vest in four equal and annual installments beginning on the first anniversary date of the grant. Remarks:

On January 28, 2025, the Reporting Person filed a Form 4 which inadvertently understated, by 360 shares, the number of shares received upon the settlement of performance stock units that were granted on March 1, 2023 under the Amended and Restated ADTRAN Holdings, Inc. 2020 Employee Stock Incentive Plan. This amendment is being filed to correct the number of shares received and the total number of shares directly held by the Reporting Person following such settlement.

As a result of this amendment, the reporting person beneficially owns a total of 955,830.51 shares as of the date hereof and not 955,470.51 shares as reported on the most recent Form 4 filed by the reporting person on January 28, 2028.

Shares delivered to the Issuer for the payment of withholding taxes due upon the vesting of previously granted performance stock units.

These shares represent the vesting of performance stock units that were awarded pursuant to a grant on May 24, 2023 under the Amended and Restated ADTRAN Holdings, Inc. 2020 Employee Stock Incentive Plan.