Stablecoin Security: The Complete Risk Guide for Issuers

By the Guardian team Updated November 2026 6 min read

Quick answer. The main risks are an unbacked mint, a stolen or misused admin key, an unsafe upgrade, a freeze that misses a path, and a misconfigured chain. Many start offchain, in the keys and services that call the contract.

Watch: Stablecoin Security: The Complete Risk Guide for Issuers 1:52

Video transcript

The main stablecoin risks are unbacked mints, stolen keys, unsafe upgrades, freezes that miss a path, and misconfigured chains. Many start offchain.

In March 2026, one compromised offchain signing key let an attacker mint 80 million unbacked USR. The contract had no mint cap.

A stablecoin is a contract plus everything that tells it what to do. Map all five layers, from mint logic to operations.

Cap mints onchain, with per-minter allowances, limits per mint and per period, and whitelisted recipients. Check output against deposit, and simulate signed mints before broadcast.

Put no high-risk operation behind a single key. Separate the role admin, minter, pauser and upgrade admin. At Zoth, a compromised admin key upgraded the proxy and moved 8.85 million dollars.

Under the GENIUS Act, issuers must be able to comply with lawful freeze orders. Test that frozen addresses cannot move value through transfers, permits, bridges or redemptions.

Watch every chain. Reconcile mints and burns against reserves, and alert on role changes, upgrades, freezes, bridge flows and access to mint keys.

Guardian has run more than 50 engagements on USDT0, Tether's omnichain stablecoin, including deployments on 25 plus chains. On Polygon, it caught a migration plan that would have left more USDT0 circulating than USDT backing it.

Read the full guide for the issuer checklist, or talk to Guardian to test your stablecoin's controls before launch.

On March 22, 2026, an attacker used one compromised signing key to mint 80 million unbacked USR, Resolv's stablecoin. Chainalysis says "the code worked exactly as intended."

Five months earlier, Paxos minted 300 trillion PYUSD by mistake and burned it within 30 minutes. Paxos said there was no security breach.

The GENIUS Act and the OCC's final rule take effect January 18, 2027. Hong Kong's HKMA set out detailed expectations in August 2025.

This article explains the technical and security side of the GENIUS Act, the OCC's rule and the HKMA guideline. It is not legal advice; confirm how it applies to you with counsel.

The Stablecoin Attack Surface

A stablecoin is a contract plus everything that tells it what to do. Map five layers:

Layer	What goes wrong	Public example
Mint and burn	Supply created without backing	Resolv, March 2026: 80M unbacked USR
Keys and roles	A key that can mint, upgrade or grant roles is taken	Zoth, March 2025: admin key upgraded the proxy
Contract code	A bug in a token function	DEUS, May 2023: a burnFrom parameter error
Chains and bridges	A wrong peer, verifier or migration	USDT0 on Polygon, August 2025: a bad migration plan, caught in review
Operations	A human or system error at issuance	PYUSD, October 2025: 300 trillion minted by mistake

Mint, Burn and Reserves

Resolv's mint had two steps: a user deposited USDC, then an offchain service holding a privileged key set the USR amount.

The attacker reached that key in Resolv's AWS KMS environment. Per Chainalysis, the contract enforced a minimum output but no maximum: no ratio check, no oracle, no cap.

About $100,000 to $200,000 in deposits became 80 million USR. USR fell as low as $0.20.

Mint limits

Limits to set:

Per-minter allowances that shrink with every mint, as in Circle's USDC contract.
A maximum per mint and per period, checked onchain.
Mints only to whitelisted addresses, one of the HKMA's example measures.
An onchain check of output against deposit, for any deposit-driven mint.
Simulation of every signed mint before it is broadcast.

Paxos shows the other half: reverse a bad mint fast.

Reserves and oracles

The rules now spell out reserve checks:

GENIUS Act: publish reserve composition monthly, have a registered public accounting firm examine it, and have the CEO and CFO certify it.
HKMA: daily statements of circulation and reserves, and attestations that test at least one randomly selected business day.

Attestations are periodic, but the contract mints in real time. Alert on any mint with no matching deposit.

A price or reserve feed that drives a mint is part of your mint control.

Roles, Keys and Upgrades

The HKMA lists the operations to cover: deploy, configure, mint, burn, upgrade, pause, blacklist, freeze and more.

For each, it expects an authorization level proportionate to risk, and high-risk operations designed so no single party can perform them alone.

The OCC's rule requires appropriate segregation of duties and dual controls, and measures for private key management, backup and recovery.

Separate the roles:

Role admin: the highest threshold. The HKMA says no staff member should have full control over role management.
Minter: LayerZero's Stablecoin OFT docs say to grant it only to the OFT contract, "never to EOAs."
Pauser and unpauser: on different multisigs, as LayerZero advises. Pausing should be fast; undoing a pause, harder.
Upgrade admin: separate from the owner. In USDC, only the admin role can upgrade.

The HKMA also expects keys that deploy, upgrade, manage roles or make large mints and burns to be generated offline, in an air-gapped environment.

Upgrades

An upgrade replaces the code every holder trusts. In March 2025, an attacker with Zoth's compromised admin key upgraded its proxy and moved $8.85M, DefiLlama records.

The HKMA expects a qualified third-party audit at least yearly and on every deployment, redeployment or upgrade.

The OCC requires processes to ensure key systems, "including smart contracts, are operating as intended," plus periodic independent testing.

Freeze, Blacklist and Pause

Under the GENIUS Act, an issuer may issue only if it has the technological capability to comply, and will comply, with lawful orders. The Act defines those as orders to seize, freeze, burn or prevent the transfer of its coins.

Speed decides whether a freeze works. After draining exchange Grinex in April 2026, attackers swapped USDT at once "to defeat stablecoin freezes," DefiLlama records.

Test that a frozen address cannot move value through:

transfer and transferFrom, as sender, recipient or spender
permits and existing allowances
bridge sends, and receipts on the destination chain
redemption and burn paths, on every chain

Know what a pause stops. In USDC, pause blocks transfers, minting and burning, while blacklist changes, role changes and upgrades still work.

Our freeze requirements comparison maps the MAS, HKMA and GENIUS texts to a role design.

Multichain Deployments

Each new chain adds contracts, keys and a messaging path that can create supply.

LayerZero warns that with one DVN (message verifier), a single operator can "forge messages that were never sent on the source chain." It sets a floor of two independent DVNs.

Its Stablecoin OFT adds outbound rate limits, which "cap the contagion risk to other chains."

On Polygon in August 2025, Guardian found a migration plan that would have left more USDT0 circulating than USDT backing it. It was fixed before the transactions ran.

Our multichain verification and OFT security checklists cover each chain.

Monitoring and Response

The HKMA expects continuous monitoring of the underlying technology's availability and performance, and procedures for incidents.

Chainalysis's lesson from Resolv: alert on mints out of proportion to collateral, and pause automatically.

Watch, on every chain:

every mint and burn, against the reserve ledger
role grants, ownership changes and upgrades
blacklist, freeze and pause events
supply moving across bridges
access to the cloud and signing services that hold mint keys

Then decide who can pause each chain, and how to reach them at any hour.

Issuer checklist

Inventory every privileged function on every chain, and who holds it.
Cap mints onchain: per minter, per call and per period.
Put no high-risk operation behind a single key.
Generate mint, upgrade and role keys offline, and test recovery.
Audit every deployment and upgrade, and match bytecode to the audit.
Test that a freeze blocks every path, on every chain.
Reconcile supply on every chain against reserves, daily.
Rehearse a pause and a bad mint on a fork.

See our stablecoin regulation guide for what each market requires.

How Guardian Helps

Since January 2025, Guardian has run more than 50 engagements on USDT0, Tether's omnichain stablecoin.

They span the code, deployments on 25+ chains, the multisig and offchain infrastructure.

OneSig: Guardian found signed transactions could be replayed on a forked chain to execute privileged actions twice.
USAT: bytecode matched byte-exact on two networks, plus a 62-test fork suite over blocklist, permit, mint and redeem paths.
Gasolina: a review of the offchain signer in USDT0's cross-chain path.

For a new coin, Guardian's institutional work starts with architecture, roles and key custody.

Once live, Managed Security monitors your contracts on every block, and reviews every multisig transaction before it is signed.

Frequently Asked Questions

What are the main security risks for a stablecoin issuer?

Unbacked mints, stolen or misused admin keys, unsafe upgrades, freezes that miss a transfer path, and misconfigured chains. Resolv's March 2026 loss came from one compromised offchain signing key, with no mint cap in the contract.

How should stablecoin minting be controlled?

Cap mints in the contract: per-minter allowances, per-mint and per-period limits, and whitelisted recipient addresses. Keep mint keys behind multiple approvals, simulate signed mints before broadcast, and reconcile every mint against reserves.

Do regulators require stablecoin smart contract audits?

The HKMA expects a qualified third-party audit at least yearly and on every deployment, redeployment or upgrade. For issuers it supervises, the OCC's rule requires processes to ensure smart contracts operate as intended, plus periodic independent testing.

Who should hold the freeze and pause roles?

Signers separate from the minter and upgrade admin, reachable at any hour. Put pauser and unpauser on different multisigs, as LayerZero advises, so a pause is fast and undoing one is harder.

Sources

Test your stablecoin's controls before launch

Guardian reviews your mint path, roles, keys, freeze design and every chain deployment, the same layers it has covered across USDT0.

Talk to Guardian Explore Guardian for institutions