Form 8-K

8-K — Tenable Holdings, Inc.

Accession: 0001660280-26-000042

Filed: 2026-10-06

Period: 2026-10-05

CIK: 0001660280

SIC: 7372 (SERVICES-PREPACKAGED SOFTWARE)

Item: Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

Item: Regulation FD Disclosure

Item: Financial Statements and Exhibits

Documents

8-K — tenb-20261005.htm (Primary)

EX-99.1 (a100626pressrelease.htm)

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8-K

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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): October 5, 2026

__________________

TENABLE HOLDINGS, INC.

(Exact name of registrant as specified in its charter)

__________________

Delaware 001-38600 47-5580846

(State or other jurisdiction of incorporation or organization) (Commission File Number) (I.R.S. Employer Identification Number)

6100 Merriweather Drive, Columbia, Maryland, 21044

(Address of principal executive offices, including zip code)

(410) 872-0555

(Registrant’s telephone number, including area code)

__________________

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, par value $0.01 per share TENB The Nasdaq Stock Market LLC

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 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On October 5, 2026, upon the recommendation of its Nominating and Corporate Governance Committee, the Board of Directors (the “Board”) of Tenable Holdings, Inc. (the “Company”) approved an increase in the size of the Board from 10 to 11 directors, and appointed Charles Bell to serve as a director of the Company, effective October 5, 2026. Mr. Bell will serve as a Class III director whose term will expire at the 2027 Annual Meeting of Stockholders, and he has been appointed to serve as a member of the Cybersecurity Risk Management Committee of the Board (“Cybersecurity Committee”).

There is no arrangement or understanding between Mr. Bell and any other person pursuant to which he was selected as a director of the Company, and there is no family relationship between Mr. Bell and any of the Company’s other directors or executive officers. The Company is not aware of any transaction involving Mr. Bell requiring disclosure under Item 404(a) of Regulation S-K. Additional information about Mr. Bell is set forth below:

Charles Bell, age 68, currently serves as Executive Vice President, Engineer, at Microsoft Corporation (“Microsoft”), a position he has held since February 2026. He previously served as Executive Vice President, Security, Compliance, Identity, and Management at Microsoft from September 2021 to February 2026. Prior to joining Microsoft, Mr. Bell spent more than two decades at Amazon.com, Inc., where he served in several roles, including Senior Vice President of Amazon Web Services. Earlier in his career, Mr. Bell began as an engineer at The Boeing Company, working on the Space Shuttle program, before joining Oracle Corporation, where he became Director of Professional Services. Mr. Bell has served on the board of directors of Twilio Inc. since March 2023. He holds a Bachelor of Science in Business Administration and Computer Science from California State University, Fullerton. The Board believes Mr. Bell is qualified to serve as a director based on his deep technical expertise in enterprise software and security systems, his extensive leadership experience scaling large-scale cloud infrastructure and cybersecurity organizations, and his experience serving as a public company director.

Upon commencement of his service as a director on October 5, 2026, the Board granted Mr. Bell 10,386 restricted stock units ("RSUs"). The RSUs will vest in three equal annual installments on each anniversary of the grant date, subject to Mr. Bell’s continued service as a director through the applicable vesting dates and accelerated vesting in specified circumstances.

Additionally, the Board approved the following compensation for Mr. Bell for his service on the Board and the Cybersecurity Committee for the year ending December 31, 2026, which will be prorated for his 2026 service and subject to his continued service through the applicable payment dates:

•Board Service Retainer: $35,000

•Cybersecurity Committee Member Service Retainer: $5,000

Mr. Bell has also entered into the Company’s standard form of indemnification agreement.

Item 7.01 Regulation FD Disclosure.

On October 6, 2026, Tenable issued a press release relating to the appointment of Mr. Bell to the Board. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

The information in this Item 7.01 of this Current Report on Form 8-K (including Exhibit 99.1) is furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or subject to the liabilities of that section or Sections 11 and 12(a)(2) of the Securities Act of 1933, as amended. The information shall not be deemed incorporated by reference into any other filing with the Securities and Exchange Commission made by the Company, whether made before or after today’s date, regardless of any general incorporation language in such filing, except as shall be expressly set forth by specific references in such filing.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

Exhibit Number Description

99.1

Press Release dated October 6, 2026

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The cover page from Tenable's 8-K filed on October 6, 2026, formatted in Inline XBRL.

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.

TENABLE HOLDINGS, INC.

Date: October 6, 2026 By: /s/ Michelle VonderHaar

Michelle VonderHaar

Chief Legal Officer and Corporate Secretary

EX-99.1

Filename: a100626pressrelease.htm · Sequence: 2

Document

Tenable Appoints Industry Veteran Charlie Bell to Board of Directors

Former Microsoft and AWS executive brings decades of product engineering, cloud security and infrastructure expertise to accelerate Tenable’s AI-powered exposure management leadership

COLUMBIA, Md. (October 6, 2026) — Tenable® Holdings, Inc. (NASDAQ: TENB), the exposure management company, today announced the appointment of Charlie Bell to its Board of Directors. A seasoned technology executive with nearly four decades of hands-on software engineering and operational leadership, Bell brings deep expertise in building and scaling complex cloud systems to Tenable’s board as the company continues to advance its AI-powered exposure management platform.

Bell’s appointment comes at a crucial inflection point for the enterprise cybersecurity industry. As organizations navigate the convergence of AI integration, cloud infrastructure and an accelerating volume of software vulnerabilities, Bell’s engineering-first perspective and extensive background in cloud-scale product architecture will reinforce Tenable’s strategic direction.

“Charlie Bell is one of the foundational architects of modern cloud computing and enterprise security,” said Mark Thurmond, Co-CEO of Tenable. “His track record of engineering resilient, large-scale software platforms and leading world-class product teams is phenomenal for our business.”

"Charlie brings deep experience leading organizations through major technology shifts, from the rise of cloud computing at massive scale to the security transformations that followed. He'll bring that same judgment to Tenable as we lead the security market into this next era of AI-driven exposure management and proactive risk reduction," said Steve Vintz, Co-CEO of Tenable.

Bell spent over two decades at Amazon Web Services (AWS), playing a central role in building its cloud infrastructure from its inception into a global, multi-billion dollar business. As a Senior Vice President at AWS, he led core engineering, utility computing and operational teams responsible for scaling cloud platforms used by millions of enterprises worldwide. Most recently, Bell served as Executive Vice President of Security, Compliance, Identity and Management at Microsoft, where he oversaw the company's enterprise security strategy, product engineering and threat intelligence operations.

"Tenable has established itself as the pioneer in exposure management, helping organizations focus on the risks that actually matter before they’re exploited," said Bell. "Throughout my career, I’ve been driven by a conviction that great engineering is the foundation of effective security. Tenable’s vision, backed by its massive data lake and advanced exposure intelligence, positions it uniquely to address the complexities of today’s AI attack surface. I look forward to working alongside the executive leadership team and the board to help guide the company's next phase of engineering-driven growth."

With Bell's appointment, Tenable strengthens its board's technical depth, ensuring the company remains positioned to help global organizations reduce risk across AI, cloud, identity, OT and traditional IT environments.

About Tenable

Tenable® is the exposure management company, exposing and closing the cybersecurity gaps that erode business value, reputation and trust. The company’s AI-powered exposure management platform radically unifies security visibility, insight and action across the attack surface, equipping modern organizations to protect against attacks from IT infrastructure to cloud environments to critical infrastructure and everywhere in between. By protecting enterprises from security exposure, Tenable reduces business risk for over 40,000 customers around the globe. Learn more at tenable.com.

Media Contact:

Tenable PR

tenablepr@tenable.com

Forward-Looking Statements

This press release contains “forward-looking” statements, as that term is defined under the federal securities laws, including statements regarding the impact of the appointment of Charlie Bell to Tenable’s Board of Directors, anticipated strategic benefits and contributions to Tenable’s product development, platform engineering and AI-powered exposure management leadership, and future growth. Forward-looking statements are subject to a number of risks and uncertainties, many of which involve factors or circumstances that are beyond Tenable’s control. Tenable’s actual results could differ materially from those stated or implied in forward-looking statements due to a number of factors, including risks and uncertainties related to the development, integration and performance of advanced AI technologies, market acceptance of Tenable’s exposure management platform, and other risks detailed in Tenable’s Form 10-K filed with the Securities and Exchange Commission (“SEC”) for the year ended December 31, 2025, in Tenable’s quarterly reports on Form 10-Q for the quarters ended March 31, 2026 and June 30, 2026 and in other filings and reports that Tenable may file from time to time with the SEC. The forward-looking statements included in this press release represent Tenable’s views as of the date of this press release. Tenable anticipates that subsequent events and developments will cause Tenable’s views to change. Tenable undertakes no intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise. These forward-looking statements should not be relied upon as representing Tenable’s views as of any date subsequent to the date of this press release.

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