Company: TENB
Filing Date: 2025-04-16
Form Type: DEFA14A
Source: 0001660280-25-000066
Chunk: 0

Company: Tenable Holdings, Inc.
Filing Date: 2025-04-16
Form: DEFA14A
Chunk 0
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### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### SCHEDULE 14A

#### Proxy Statement Pursuant to Section 14(a) of the

#### Securities Exchange Act of 1934
<div align='center'>(Amendment No.)</div>

Filed by the Registrant ý

Filed by a Party other than the Registrant ¨

Check the appropriate box:

¨ Preliminary Proxy Statement

¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

¨ Definitive Proxy Statement

ý Definitive Additional Materials

¨ Soliciting Material Pursuant to § 240.14a-12

#### Tenable Holdings, Inc.
<div align='center'>(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)</div>

Payment of Filing Fee (Check the appropriate box)

ý No fee required.

¨ Fee paid previously with preliminary materials.

¨ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

#### TENABLE HOLDINGS, INC
#### .

#### 6100 Merriweather Drive, 12th Floor

#### Columbia, Maryland 21044

### SUPPLEMENT TO THE DEFINITIVE PROXY STATEMENT

#### FOR THE 2025 ANNUAL MEETING OF STOCKHOLDERS

#### May 14, 2025
This proxy statement supplement (this “Proxy Supplement”) amends and supplements the definitive proxy statement on Schedule 14A (the “Proxy Statement”) of Tenable Holdings, Inc. (the “Company”) filed with the Securities and Exchange Commission (“SEC”) on April 3, 2025 in connection with the solicitation of proxies by the Company’s Board of Directors (the “Board”) for its 2025 Annual Meeting of Stockholders to be held virtually on May 14, 2025 at 1:00 p.m. Eastern Time (the “Annual Meeting”).

The purpose of this Proxy Supplement is to provide subsequent information relating to the Board’s appointment of each of Stephen A. Vintz and Mark Thurmond to serve as Co-Chief Executive Officers of the Company on a permanent basis. Except as updated by this Proxy Supplement, all information set forth in the Proxy Statement remains unchanged. This Proxy Supplement should therefore be read in