ADTRAN Holding, Inc.: Release according to Article 40, Section 1 of the WpHG
(the German Securities Trading Act) with the objective of Europe-wide
distribution

EQS Voting Rights Announcement: Adtran Holdings, Inc.
ADTRAN Holding, Inc.: Release according to Article 40, Section 1 of the WpHG
(the German Securities Trading Act) with the objective of Europe-wide
distribution

05.09.2026 / 08:42 CET/CEST
Dissemination of a Voting Rights Announcement transmitted by EQS News - a
service of EQS Group.
The issuer is solely responsible for the content of this announcement.

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Notification of Major Holdings

1. Details of issuer

     Name:                             Adtran Holdings, Inc.
     Street:                           901 Explorer Boulevard
     Postal code:                      35806
     City:                             Huntsville
                                       United States
     Legal Entity Identifier (LEI):    549300VV36J86CRRWF77

2. Reason for notification

   X    Acquisition/disposal of shares with voting rights
        Acquisition/disposal of instruments
        Change of breakdown of voting rights
   X    Other reason:
        voluntary group notification with triggered threshold on subsidiary
        level

3. Details of person subject to the notification obligation

     Legal entity: Morgan Stanley
     City of registered office, country: Wilmington, Delaware, United
     States of America (USA)

4. Names of shareholder(s)
holding directly 3% or more voting rights, if different from 3.

Morgan Stanley & Co. LLC

5. Date on which threshold was crossed or reached:

28 Aug 2026

6. Total positions

               % of voting  % of voting rights   Total of  Total number of
           rights attached             through  both in %    voting rights
                 to shares  instruments (total    (7.a. +      pursuant to
           (total of 7.a.)   of 7.b.1 + 7.b.2)      7.b.)     Sec. 41 WpHG
  New               3.67 %              3.29 %     6.96 %         81481407
  Previo-           3.46 %              3.31 %     6.77 %                /
  us
  notifi-
  cation

7. Details on total positions
a. Voting rights attached to shares (Sec. 33, 34 WpHG)

    ISIN            Absolute                 In %
                  Direct (Sec.  Indirect  Direct (Sec.  Indirect (Sec.
                      33 WpHG)  (Sec. 34      33 WpHG)        34 WpHG)
                                   WpHG)
    US00486H1059             0   2990176           0 %          3.67 %
    Total           2990176                 3.67 %

b.1. Instruments according to Sec. 38 (1) no. 1 WpHG

    Type of instrument    Expiration   Exercise or    Voting  Voting
                          or maturity  conversion     rights  rights
                          date         period       absolute    in %
    Right of recall over  at any time  at any time   1625225  1.99 %
    securities lending
    agreements
                                       Total         1625225  1.99 %

b.2. Instruments according to Sec. 38 (1) no. 2 WpHG

    Type of    Expiration   Exercise or  Cash or       Voting  Voting
    instrume-  or maturity  conversion   physical      rights  rights
    nt         date         period       settlement  absolute    in %
    Converti-  15.09.2030   at any time  Physical     1057043   1.3 %
    ble Bond
                                         Total        1057043   1.3 %

8. Information in relation to the person subject to the notification
obligation

        Person subject to the notification obligation is not controlled nor
        does it control any other undertaking(s) that directly or
        indirectly hold(s) an interest in the (underlying) issuer (1.).
   X    Full chain of controlled undertakings starting with the ultimate
        controlling natural person or legal entity:

  Name               % of voting       % of voting rights  Total of both
                   rights (if at  through instruments (if   (if at least
                     least 3% or     at least 5% or more)    5% or more)
                           more)
  Morgan Stanley               %                        %              %
  Morgan Stanley               %                        %              %
  Capital
  Management, LLC
  Morgan Stanley               %                        %              %
  Domestic
  Holdings, LLC
  Morgan Stanley               %                        %              %
  Capital
  Services LLC
  -                            %                        %              %
  Morgan Stanley               %                        %              %
  Morgan Stanley               %                        %              %
  Capital
  Management, LLC
  Morgan Stanley          3.02 %                        %          5.5 %
  & Co. LLC
  -                            %                        %              %
  Morgan Stanley               %                        %              %
  Morgan Stanley               %                        %              %
  International
  Holdings Inc.
  Morgan Stanley               %                        %              %
  International
  Limited
  Morgan Stanley               %                        %              %
  Investments
  (UK)
  Morgan Stanley               %                        %              %
  & Co.
  International
  plc
  -                            %                        %              %
  Morgan Stanley               %                        %              %
  Morgan Stanley               %                        %              %
  Capital
  Management, LLC
  Morgan Stanley          3.02 %                        %          5.5 %
  & Co. LLC
  Prime Dealer                 %                        %              %
  Services Corp.
  -                            %                        %              %
  Morgan Stanley               %                        %              %
  Morgan Stanley               %                        %              %
  Capital
  Management, LLC
  Morgan Stanley               %                        %              %
  Smith Barney
  LLC

9. In case of proxy voting according to Sec. 34 para. 3 WpHG
(only in case of attribution of voting rights in accordance with Sec. 34
para. 1 sent. 1 No. 6 WpHG)

Date of general meeting:
Holding total positions after general meeting (6.) after annual general
meeting:

     Proportion of voting    Proportion of    Total of
                   rights      instruments        both
                        %                %           %

10. Other explanatory remarks:

   The notification was triggered mainly due to an acquisition of shares
   with voting rights, in addition to an acquisition of client securities
   over which Morgan Stanley & Co. LLC has a right of use.

Date

02 Sep 2026


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05.09.2026 CET/CEST The EQS Distribution Services include Regulatory
Announcements, Financial/Corporate News and Press Releases.
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   Language:    English
   Company:     Adtran Holdings, Inc.
                901 Explorer Boulevard
                35806 Huntsville
                United States
   Internet:    www.adtran.com
   LEI Code:    549300VV36J86CRRWF77

End of News EQS News Service
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2394526 05.09.2026 CET/CEST