Tenable Holdings Set to Join S&P SmallCap 600

Tenable Holdings (NASD: TENB) will be added to the S&P SmallCap 600, replacing Leggett & Platt (NYSE: LEG), effective prior to the open on August 31, 2026, according to S&P Dow Jones Indices.

Rhea-AI Summary

Tenable Holdings (NASD: TENB) will be added to the S&P SmallCap 600, replacing Leggett & Platt (NYSE: LEG), effective prior to the open on August 31, 2026, according to S&P Dow Jones Indices. Leggett & Platt is being acquired by Somnigroup International (NYSE: SGI), a constituent of the S&P MidCap 400, in a transaction expected to close soon, subject to final conditions.

The index change will place Tenable in the Information Technology sector within the S&P SmallCap 600, while Leggett & Platt, classified in Consumer Discretionary, will be deleted from that index on the same effective date.

Positive

• Tenable added to S&P SmallCap 600 effective August 31, 2026
• Somnigroup acquiring Leggett & Platt, triggering index rebalancing

Negative

• Leggett & Platt removed from S&P SmallCap 600 on August 31, 2026

Argus Aug 27 session 114 alerts

+11.76% close to close 22.6x rel. volume Open Argus

Details

News Market Reaction – TENB

+7.2% Peak in 7 hr 45 min

$4.23B Market Cap

On Aug 27, the first trading day after this news, TENB closed 11.76% above the previous close. Argus tracked a peak move of +7.2% during that session. Our momentum scanner recorded 114 alerts for this stock that day. Relative volume reached 22.6x the daily average during tracking.

Data tracked by StockTitan Argus for the Aug 27 session.

Key Figures

Effective Date: August 31, 2026

Effective Date

August 31, 2026

S&P SmallCap 600 addition before market open

Historical Context

5 past events · Latest: Aug 26

5 events

1. Aug 26

   Cybersecurity research

   24h Move

   +2.6%

   Joint research identified vendor-ecosystem targeting and reported 79% exposure-runtime alignment.

2. Aug 10

   Investor conference

   24h Move

   +0.9%

   Leadership presentations at two scheduled investor conferences preceded a 0.88% reaction.

3. Aug 04

   AI platform launch

   24h Move

   +2.8%

   Company launched an open-source AI-agent exchange with more than 50 components available.

4. Aug 04

   AI security expansion

   24h Move

   +2.8%

   AI security coverage expanded across major platforms after 457 million issues detected.

5. Jul 29

   Q2 earnings report

   24h Move

   +3.4%

   Q2 revenue exceeded expectations, and management raised the full-year outlook.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

s&p smallcap 600, gics sector

2 terms

s&p smallcap 600 financial

"Tenable Holdings Inc. will replace Leggett & Platt Inc. in the S&P SmallCap 600"

A stock market index made up of 600 small-cap U.S. companies chosen to represent the performance of smaller publicly traded firms. It matters to investors because it acts like a temperature gauge for the small-company segment of the market, serving as a benchmark for fund managers, a basis for index funds and ETFs, and a way to compare returns and risk when building a diversified portfolio.

gics sector financial

"Company Name | Ticker | GICS Sector"

GICS sector is one of the major industry groupings from the Global Industry Classification Standard, a system that sorts companies into consistent categories (like Technology or Health Care) based on the primary business they do. Investors use these sectors like folders in a filing cabinet to compare companies, build diversified portfolios, and track how whole parts of the market are performing rather than focusing on single stocks.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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NEW YORK, Aug. 26, 2026 /PRNewswire/ -- Tenable Holdings Inc. (NASD: TENB) will replace Leggett & Platt Inc. (NYSE: LEG) in the S&P SmallCap 600 effective prior to the opening of trading on Monday, August 31. S&P MidCap 400 constituent Somnigroup International Inc. (NYSE: SGI) is acquiring Leggett & Platt in a deal expected to be completed soon, pending final closing conditions.

Following is a summary of the changes that will take place prior to the open of trading on the effective date:

Effective Date	Index Name		Action	Company Name	Ticker	GICS Sector
Aug 31, 2026	S&P SmallCap 600	Addition		Tenable Holdings	TENB	Information Technology
Aug 31, 2026	S&P SmallCap 600	Deletion		Leggett & Platt	LEG	Consumer Discretionary

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SOURCE S&P Dow Jones Indices

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

When will Tenable Holdings (TENB) join the S&P SmallCap 600 index?

Tenable Holdings will join the S&P SmallCap 600 before trading opens on August 31, 2026. According to S&P Dow Jones Indices, Tenable will be added as an Information Technology company during this index rebalancing, replacing Leggett & Platt.

Which company is Tenable Holdings (TENB) replacing in the S&P SmallCap 600 on August 31, 2026?

Tenable Holdings will replace Leggett & Platt (LEG) in the S&P SmallCap 600 on August 31, 2026. According to S&P Dow Jones Indices, Leggett & Platt will be deleted from the index due to its pending acquisition.

Why is Leggett & Platt (LEG) being removed from the S&P SmallCap 600 index?

Leggett & Platt is being removed because it is being acquired by Somnigroup International (SGI). According to S&P Dow Jones Indices, this acquisition, expected to close soon pending final conditions, triggers Leggett & Platt’s deletion from the S&P SmallCap 600.

What sector classification will Tenable Holdings (TENB) have in the S&P SmallCap 600?

Tenable Holdings will be classified in the Information Technology sector within the S&P SmallCap 600. According to S&P Dow Jones Indices, this sector assignment reflects Tenable’s business profile as it enters the index on August 31, 2026.

How does Somnigroup International (SGI) factor into the S&P index changes involving LEG and TENB?

Somnigroup International, an S&P MidCap 400 constituent, is acquiring Leggett & Platt. According to S&P Dow Jones Indices, this pending acquisition leads to Leggett & Platt’s removal from the S&P SmallCap 600 and the simultaneous addition of Tenable Holdings.

Will Somnigroup International (SGI) change indexes after acquiring Leggett & Platt (LEG)?

The announcement does not state any index change for Somnigroup International. According to S&P Dow Jones Indices, SGI remains an S&P MidCap 400 constituent while acquiring Leggett & Platt, which is being removed from the S&P SmallCap 600.