DeFi insurance: what it covers, costs and who underwrites it

DeFi insurance is a small, discretionary market that prices cover in low single-digit percentages a year, and the capital behind it increasingly sits in vaults that earn the premiums buyers pay.

DeFi insurance lets a holder pay a premium for cover against a defined failure, such as a smart contract hack, an oracle failure or a custodian halting withdrawals. Most of it is written by discretionary mutuals and parametric protocols that pool underwriters' capital onchain, and the market is small next to what it protects. On 27 September 2026, insurance protocols tracked by DefiLlama held $130.1 million against $95.7 billion locked across DeFi, and Nexus Mutual alone accounted for $114.7 million of it.

Whether a policy pays out depends on what its wording covers, how much cover is left to buy and who decides claims. On 27 September 2026, Nexus Mutual quoted cover for Aave v3 at 0.88% to 2.85% a year, with about $15 million of capacity left for new buyers. That capacity comes from underwriters who stake capital, collect the premiums and pay the claims, so for them underwriting works much like any other yield strategy, and it can be run inside a vault.

Common DeFi insurance terms

How does DeFi insurance work?

A buyer picks a listing (a protocol, a vault, a stablecoin or a custodian), chooses an amount and a period, and pays the premium upfront or as a stream. The premium goes to the underwriters whose capital backs that listing, and the capital itself sits in a pool the provider controls onchain. If a covered event happens, the buyer files a claim with proof of loss, the provider assesses it against the wording, and an approved claim is paid out of the pool.

Nexus Mutual shows the moving parts clearly. Underwriters stake the mutual's NXM token into staking pools run by pool managers, who choose which listings to back and at what minimum price. According to the Nexus Mutual FAQ, every 1 NXM staked opens 2 NXM of capacity, half of each cover fee goes to the stakers who underwrote it, and half of each paid claim is met by burning those stakers' NXM, with the other half shared across all NXM holders. Buyers must become members, which involves KYC, and can cover assets held in other wallets they control.

Discretionary mutuals vs parametric cover

The two main designs trade certainty of payout against breadth of cover. A discretionary mutual can cover messy events like a custodian freezing withdrawals, and it keeps the right to decline a claim that falls outside the wording. A parametric policy pays the moment its trigger is hit, and it only ever pays for the trigger it names.

A discretionary mutual works like a neighbourhood fund whose members read each claim and vote on whether to pay it. Parametric cover works like flight-delay insurance, which pays once the airline's records show a delay past a set limit. DeFi versions swap the neighbours for a claims committee and the airline's records for a price feed.

Claims decisions at Nexus have moved from token-holder votes to named experts. The mutual's claim assessment documentation says a Claims Committee of three publicly known assessors has decided every claim since November 2025, with 2 of 3 votes needed inside a 72-hour window, followed by a 24-hour cool-down for fraud checks. From 2019 to March 2023, any member staking NXM could vote, subject to a 70% consensus threshold.

What DeFi insurance covers and what it excludes

Protocol cover is the most common product, and its wording is narrow on purpose. Nexus Mutual's Multi Protocol Cover lists smart contract exploits, oracle failure, oracle manipulation, liquidation failure and governance takeovers as covered events. It excludes loss of asset value such as a depeg, losses from phishing, private key breaches or malware, and frontend attacks where the protocol itself is unaffected.

• Protocol cover: loss of funds deposited in named protocols from technical failures and attacks.
• Depeg cover: a stablecoin trading below a set level, often parametric. Nexus listed Sky USDS depeg cover at 0.50% a year on 27 September 2026.
• Custody cover: a centralised exchange or custodian halting withdrawals or losing funds. Nexus priced Coinbase and Kraken custody cover at 1.75% a year on the same day.
• Slashing cover: penalties on staked ETH or other proof-of-stake assets.
• Fund and vault cover: bespoke policies over a manager's whole portfolio, or cover attached to a vault's shares.

The claims rules matter as much as the list. Multi Protocol Cover makes a claimant wait 14 days after a loss event before filing, allows filing up to 35 days after the cover expires, and applies a default 5% deductible, so a buyer with 100 ETH of cover absorbs the first 5 ETH. The distinction between loss of funds and loss of value decided the biggest test the market has faced: when UST collapsed in May 2022, CryptoSlate reported that Nexus protocol cover on Anchor was unlikely to pay, because it covered "a loss of funds, not a loss of value", while depeg policies paid.

DeFi insurance providers

The concentration stands out. Of the $130.1 million DefiLlama counts across 31 insurance protocols, Nexus Mutual holds about 88%, and several once-prominent names now hold under $1 million. Nexus itself is down from $780.6 million at its November 2021 peak. For buyers, the practical choice for large amounts is mostly Nexus capacity, bought directly or through OpenCover.

Claims history

Nexus Mutual reports more than $18.5 million paid across 103 claims as of August 2026. Its public claims ledger lists each one, and the largest cover both onchain hacks and centralised failures.

Set against the losses, the payouts are small. Euler lost about $197 million and Nexus paid $2.4 million, because only depositors who had bought cover were paid, and only up to the amount each had covered. DeFi insurance has paid real claims for a long time, and it has only ever covered a sliver of the money at risk.

How much does DeFi insurance cost?

Nexus prices each listing inside each staking pool. Pool managers set a target price, the price starts from an initial level set by the Advisory Board, and each purchase bumps it up by 0.05% for every 1% of the pool's capacity it uses, according to the Nexus pricing documentation. With no new purchases, the price decays back toward the target, so a rush of buyers before an expected loss pays more for the same cover.

Nexus Mutual capacity API, 27 September 2026. Prices differ across the staking pools behind each listing and rise with the size of a purchase, and the range shows the lowest and highest annual price returned. Cover on a large lending market takes a real bite out of its yield: Aave's Ethereum USDC market paid lenders 3.62% on 24 September 2026, so cover at 0.88% would absorb about a quarter of the DeFi lending return. Newer or more complex protocols cost more, and the price scales with how much of a listing a buyer wants.

Capacity limits

Capacity is the hard ceiling. The capacity figures above are shared across the mutual's pools and aren't additive, and some listings have none: Nexus's Multi Protocol Cover listing for a MetaMorpho setup returned no available capacity on 27 September 2026 and invited buyers to request more. OpenCover's Covered Vaults cap cover at about $50 million per vault, and most of its stablecoin vaults had between $1.5 million and $7 million of cover in use on the same day. A treasury with $100 million in a single protocol will usually find it can cover a fraction of it, and only by splitting purchases across listings and time.

The risks of relying on DeFi insurance

Cover moves some risk to someone else and adds a few risks of its own. The provider can decline a claim that falls outside the wording, and Nexus states in its FAQ that its cover "is not a contract of insurance" and carries no legal obligation to pay. A large correlated event, such as a widely used protocol failing, could produce claims larger than the capital backing them, and the provider's own contracts can have bugs.

• Wording risk: a loss outside the listed events, such as a depeg under protocol cover, isn't paid.
• Solvency risk: claims are paid from a finite pool, and several listings share the same staked capital.
• Basis risk: parametric cover pays on the trigger, which may not match the buyer's actual loss.
• Regulatory status: most DeFi cover isn't regulated insurance (per Nexus Mutual's FAQ and OpenCover's guide), so a buyer relies on the provider's discretion to pay.
• Timing: waiting periods, filing windows and deductibles delay and reduce payouts.

Always make sure to do your own research and be aware of the above and any other risks before depositing.

Underwriting vaults: where insurance capital earns premiums

Every policy needs capital on the other side, and that capital earns the premiums. Underwriting has historically meant buying a protocol's token and staking it, which ties the underwriter's return to the token price. The newer structure puts the underwriting capital in a vault that takes deposits in a stablecoin, allocates that money to back policies, streams the premiums back to depositors as yield, and takes the loss when a claim is paid.

Both sides of this are live. On the capital side, the Nexus Mutual RWI Vault takes USDC to back real-world insurance contracts with carefully selected partners, offering a 6% fixed baseline APY that is itself protected by Nexus cover, with $2 million deposited and $8 million of its cap remaining on 27 September 2026. It's open only to accredited and sophisticated investors after KYC, withdrawals are estimated at 90 days, and Nexus tells depositors to expect an 18 to 24 month timeframe for returns. On the buyer side, OpenCover launched Covered Vaults in April 2026, letting depositors activate cover by depositing their vault shares and streaming the premium out of the vault's yield, and its Covered Vaults interface listed more than 20 covered vaults on 27 September 2026. Ensuro runs the same capital model for insurance partners' portfolios, with $2.1 million deposited according to DefiLlama.

An underwriting vault asks for the same controls as any other vault, applied more strictly. The capital has to stay liquid enough to pay claims, so it can only sit in assets and protocols the mandate allows. Withdrawals need a lag long enough to cover the claims tail, or depositors could exit the moment a loss looks likely. The share price has to reflect claims as they are approved, and a curator or risk manager has to decide which policies the pool backs. These pieces already exist in vault infrastructure: a policy engine that limits where capital can go, separate curator and operator roles, request-based redemptions with a published lag, and onchain share accounting.

Upshift builds vaults with that structure across more than 30 chains, with a policy engine that restricts vault funds to approved protocols, tokens and functions, and contracts that have been through 10 smart contract audits by 6 independent firms. An insurer or mutual raising underwriting capital from outside depositors needs the same design that lets a curator run a stablecoin vault inside a defined mandate, which makes insurance one more financial product that can run as a vault. The risk management framework sets out how those controls are layered.

Underwriting yield carries its own risks: a large claim can wipe out months of premiums, returns can take a year or more to realise, and exits are slow by design. Always make sure to do your own research and be aware of the above and any other risks before depositing.

Frequently asked questions

What does DeFi insurance cover?

Most protocol cover pays for loss of funds from smart contract exploits, oracle failure or manipulation, liquidation failure and governance attacks. Depeg, custody and slashing cover are sold as separate products, and phishing, stolen keys and frontend attacks are usually excluded.

Is DeFi insurance real insurance?

In most cases it's an insurance alternative. Nexus Mutual's FAQ says its cover is not a contract of insurance and that claims are paid at the mutual's discretion, which is why the industry calls its products cover.

How much does DeFi insurance cost?

On 27 September 2026, Nexus quoted about 0.2% to 0.8% a year for Uniswap v3, 0.88% to 2.85% for Aave v3 and around 1.75% for major custodians. Newer protocols and larger purchases cost more.

How does Nexus Mutual work?

Members buy cover on specific listings, and NXM stakers underwrite it through staking pools that earn half of each fee. A three-person Claims Committee votes on each claim within 72 hours, and approved claims are paid from the mutual's capital pool.

Has DeFi insurance ever paid out?

Yes. Nexus Mutual reports more than $18.5 million paid across 103 claims as of August 2026, including $5.2 million after FTX halted withdrawals and $2.4 million after the Euler exploit, and InsurAce paid about $12 million after UST's collapse.

Can I earn yield by underwriting DeFi insurance?

Yes, by staking into an underwriting pool or depositing into a vault that backs policies. The return comes from premiums, and the capital is at risk when claims are paid, often with long lockups.

What is the difference between Nexus Mutual and OpenCover?

Nexus Mutual is the mutual that holds the capital, writes the wording and decides claims. OpenCover sells cover built on Nexus capacity, including Covered Vaults that attach cover to vault shares.

Keep reading

• How onchain yield vaults are secured. The roles, permissions and controls inside a vault.
• Stablecoin depegs. How depegs happen and what they cost holders.
• What are DeFi yield vaults. Strategies, risks and how to choose one.
• Segregated vs co-mingled vault accounts. How a vault's structure decides who shares a loss.
• How to tier vault strategies by risk. A framework for sorting vaults by what can go wrong.