Q3 2026's Biggest Cybersecurity Funding Rounds: Keyfactor's $1B Leads 10 Tracked Deals

Keyfactor's $1 billion private-equity investment from Summit Partners was the biggest cybersecurity funding round Value Add VC had tracked for Q3 2026 as of October 15, 2026 — leading a group of 15 tracked rounds worth $2.8 billion combined.

These are rounds tracked by Value Add VC for US and unconfirmed-HQ private companies, as of October 15, 2026; rumored rounds, public-company raises, and known non-US companies are excluded. This is not a cybersecurity market total — it's a slice of the market from the sources Value Add VC follows, meant to be compared quarter to quarter within this series rather than against PitchBook, Crunchbase, or other trackers' totals. Below are the 10 biggest rounds, ranked, each linked to its own source.

Biggest Cybersecurity Funding Rounds Q3 2026: The Full List, Ranked by Size

Tracked as of October 15, 2026, Keyfactor's $1 billion investment tops the list, followed by two $400 million rounds raised the same week in late September: Cyera's Series G extension and Island's Series F. Four of the 10 biggest rounds — Cyera, Island, Obsidian Security, and Oak — went to companies securing identity, data, or browser access, continuing the identity-and-access concentration tracked across 2026's AI cybersecurity market data.

Computed from the Value Add VC intelligence store on 2026-10-15: cybersecurity funding rounds of US and unconfirmed-HQ private companies announced in Q3 2026; rumored rounds, public-company raises, and known non-US companies excluded; one record per deal. Not a market total; each company name links its own source. How we counted: rounds Value Add VC's intelligence store had on file for Q3 2026; ranked by disclosed round size; 10 of 15 tracked deals; as of October 15, 2026.

What Was the Biggest Cybersecurity Funding Round in Q3 2026?

Keyfactor's $1 billion investment from Summit Partners, reported the week of July 10, 2026, was the largest cybersecurity round Value Add VC tracked for the quarter — more than double the size of the next two rounds on the list. The deal's structure wasn't disclosed as a priced venture round; Crunchbase's reporting describes it as a private-equity-style investment, and no post-money valuation was given.

The next two rounds, both $400 million, landed two days apart in late September: Cyera's Series G extension from Goldman Sachs Alternatives, announced September 22, 2026, and Island's Series F led by Evolution Equity Partners, announced September 24, 2026 at a $6.4 billion valuation, up $1.8 billion from Island's prior round.

Why Did Identity and Access-Control Startups Raise the Biggest Checks in Q3 2026?

Four of the 10 biggest Q3 2026 cybersecurity rounds Value Add VC tracked went to companies protecting identity, data, or access points rather than traditional network perimeter defense: Cyera (data security posture management), Island (enterprise browser isolation), Obsidian Security ($85 million Series D, $1.1 billion valuation, led by Crescent Cove Advisors per Axios, which secures SaaS identity), and Oak ($60 million seed co-led by Accel, CRV, and Greylock Partners to secure AI-agent identity). That clustering tracks with the broader pattern in AI cybersecurity attack-surface spending: as companies connect AI agents to internal systems, the access points those agents touch become the thing investors are funding defenses for.

Not every round in the top 10 named a clear lead. Horizon3.ai's $250 million Series E, reported August 3, 2026 at a $2 billion valuation, drew backing from returning investors NightDragon and New Enterprise Associates without the reporting naming a lead, and Verkada's $41.2 million raise surfaced only through a Form D filing with the SEC, which discloses the amount but not a lead investor.

How We Built This List

This ranking covers US and unconfirmed-HQ-private-company cybersecurity funding rounds in the Value Add VC intelligence store that were announced in Q3 2026 (July–September), with one record kept per deal. It excludes rumored rounds, public-company capital raises, and companies with a confirmed non-US headquarters. The store tracked 15 such rounds worth $2.8 billion combined as of October 15, 2026 — a slice of the market from the sources Value Add VC follows, not a claim to cover every cybersecurity round that closed in the quarter.

Every row above is checked against its own linked source. Three rounds the store had on file — Spur Intelligence's $200 million round, Obsidian Security's $85 million Series D, and Oak's $60 million seed — carried no source URL internally; all three are cited here to the outlets that first reported them (TechCrunch and Axios), rather than left unsourced. Obsidian Security's figures come from Axios's own reporting, since Axios's article returned a paywall block when checked for this list.

Value Add VC also publishes hand-reconciled Q3 2026 venture-funding figures, where dates and lead investors are corrected after additional review; those figures can differ slightly from this list's as-tracked totals. The full round-level log this list draws from is public at Value Add VC's funding tracker, and cybersecurity's trailing-12-month funding trend is tracked on the cybersecurity sector page.

What the headline misses

A ranked list by round size flattens very different kinds of capital events into one table. Keyfactor's $1 billion deal wasn't reported as a conventional priced venture round and disclosed no new valuation; Cyera's $400 million was an extension of an existing Series G rather than a new priced round; and three of the 10 rows (Spur Intelligence, Obsidian Security, and Oak) had no source URL in Value Add VC's own store, meaning the store's internal evidence for those three deals was weaker than for the other seven before this list's research filled the gap. Treat "10 biggest rounds" as a size ranking, not a signal that all 10 deals are comparable in structure or disclosure quality.