The June 2, 2025, exploit of Nervos Network’s ForceBridge — which resulted in the theft of $3.9 million including 539 ETH, 898,300 USDC, and 257,800 USDT — is the latest reminder that cross-chain bridges remain among the highest-risk components in the cryptocurrency ecosystem. With Bitcoin trading at $105,881 and over $114.8 million lost to crypto exploits in June alone, understanding how to evaluate bridge security is an essential skill for any serious crypto user.
The Objective
This guide provides a technical framework for evaluating cross-chain bridge security, from understanding common vulnerability classes to performing practical risk assessments before committing funds. The goal is to equip you with the knowledge to make informed decisions about which bridges to trust and how to minimize your exposure when using them.
Cross-chain bridges facilitate the transfer of assets between different blockchain networks by locking tokens on the source chain and issuing corresponding representations on the destination chain. This architecture creates a concentrated point of failure: the bridge itself holds a pool of locked assets that becomes an attractive target for attackers.
Prerequisites
Before diving into bridge security analysis, you should have a solid understanding of basic blockchain concepts including smart contracts, consensus mechanisms, and the difference between native and wrapped tokens. Familiarity with block explorers like Etherscan and basic transaction analysis is also helpful.
You will need access to a Web3 wallet, a block explorer, and ideally a tool like DeBank or Zapper that can track your positions across multiple chains. Understanding the basics of access control, multi-signature wallets, and the concept of TVL (Total Value Locked) will help you evaluate the risk profile of any bridge.
Step-by-Step Walkthrough
Step 1: Evaluate the Bridge’s Architecture. Bridges generally fall into three categories: lock-and-mint bridges (like ForceBridge), liquidity pool-based bridges, and hash time-locked contract (HTLC) bridges. Lock-and-mint bridges are the most common but also the most vulnerable, as they concentrate assets in a single smart contract. Liquidity pool bridges distribute risk but depend on sufficient liquidity on both sides. HTLC-based bridges offer atomic swaps but are limited to specific asset pairs.
The Nervos ForceBridge was a lock-and-mint design that relied on a multi-signature wallet for securing locked assets. The access control vulnerability that enabled the $3.9 million exploit demonstrates that even multi-sig protections can fail if the underlying permission structure is misconfigured.
Step 2: Check Audit History. A reputable bridge should have at least two independent security audits from recognized firms such as Trail of Bits, OpenZeppelin, Consensys Diligence, or Halborn. Check whether the audit reports are publicly available and whether any critical or high-severity findings were identified and resolved.
The Halborn team published a detailed analysis of the ForceBridge hack on June 10, 2025, confirming that the root cause was an access control issue where the attacker accessed privileged functions within the protocol’s smart contracts. This type of vulnerability should have been caught during a thorough audit.
Step 3: Assess the Security Model. Examine the bridge’s validator set, multi-signature requirements, and any time-lock mechanisms. A bridge with a small validator set (fewer than 5 signers) presents higher risk than one with a larger, decentralized set. Time-locks that delay large transactions by 24-48 hours provide a window for the community to detect and respond to suspicious activity.
Step 4: Monitor Real-Time Activity. Before executing a significant transfer, check the bridge’s current status on monitoring platforms. Tools like Cyvers Alerts, Hacken’s Extractor, and De.Fi’s REKT database track known exploits and suspicious activity across bridge protocols. If any alerts have been triggered recently, consider using an alternative bridge.
Step 5: Limit Your Exposure. Never transfer more through a bridge than you can afford to lose. For large transfers, consider splitting the transaction across multiple bridges or executing the transfer in smaller increments over time. This limits your maximum potential loss to the amount in transit at any given moment.
Troubleshooting
If a bridge transaction appears stuck or fails, do not immediately retry with a larger amount. First, verify the bridge’s operational status on its official communication channels. Check the block explorer to confirm whether your transaction was included on the source chain. If the source chain transaction succeeded but the destination chain tokens have not appeared, contact the bridge’s support team and provide the transaction hash.
If you suspect a bridge has been compromised — for example, if social media reports are emerging about unusual activity — immediately stop all interactions with the bridge and monitor the situation. In the ForceBridge case, the Nervos team paused bridge operations, but funds already in transit were lost.
Mastering the Skill
Advanced users should consider learning to read bridge smart contract code directly. Understanding how access control is implemented, how multi-signature validation works, and what happens during edge cases like chain reorganizations or gas price spikes will give you a deeper understanding of the risks involved.
Following security researchers on social media and subscribing to alert services from firms like Cyvers, Hacken, and PeckShield will keep you informed about emerging threats. The cryptocurrency security landscape evolves rapidly, and staying current is the most effective form of protection.
Disclaimer: This article is for informational purposes only and does not constitute financial or investment advice. Bridge usage involves significant risk including potential loss of funds. Always conduct your own research before using any cross-chain protocol.
nomad_survivor worms and ronin were different bugs though. worms was signature verification bypass, ronin was social engineering of validators. the pattern isnt as identical as ppl claim
$114.8M lost in June 2025 alone across all exploits. bridges account for what, 60% of that? the TVL-to-security ratio on most bridges is still laughable. check the multisig set before you cross-chain anything
tvl_risk checking multisig composition should take 5 minutes before any bridge transfer. most ppl skip it and then act surprised when a 3-of-5 multisig gets drained
G. Fischer 5 minutes is generous. most users dont even know what a multisig is let alone how to check one. UX needs to abstract this somehow
Nervos ForceBridge was a smaller exploit but the pattern is identical to Nomad and Wormhole. lock-and-mint bridges all share the same fundamental weakness
Bridges really are the Achilles’ heel of the current ecosystem. This Nervos exploit just proves that even with audits, the attack surface is massive when you’re locking up millions in a single contract. I’ve started using aggregators that split liquidity across multiple routes to minimize risk, but we still have a long way to go for true cross-chain security.
$3.9M on Nervos ForceBridge is relatively small but the pattern is the same every time. bridge contract bug, drained in minutes
same exploit pattern every single time. the bridge contract has a logic flaw and the attacker walks away before anyone notices
After losing a bit in the Nomad hack last year, I’m extremely wary of any bridge that isn’t battle-tested for at least two years. The tech is cool but nearly four million gone in an instant is a tough pill to swallow for retail users. Honestly, unless you’re moving massive volume, is the risk-reward even worth it right now?
nomad was the wake up call that nobody learned from. bridges are still moving billions with minimal multisig protection
Renars D. nomad was the wakeup call and then Wormhole happened and then Ronin happened. nobody learns. $3.9M on Nervos is small but its the same class of bug every single time
Super helpful breakdown on how to actually check the bridge health yourself. I never thought to look at the multisig composition or the TVL-to-security ratio before. Definitely going to be more careful with where I’m moving my stash next time! Thanks for the deep dive on the Nervos incident.
the lock and mint model creates an irresistible honeypot. every bridge is one audit miss away from the next exploit
Tomoko the lock-and-mint model is fundamentally broken. youre creating a centralized honeypot on both chains. light client bridges or ZK proofs are the only long term answer
relay_max light client bridges are years away from production. until then the multisig + timelock model is what we have. just keep amounts small per bridge