Gravity Bridge Key Compromise Incident Investigation Report
Date: May 30, 2026 (Publicly Disclosed June 1)
Loss Amount: ~$5.4M
Attack Type: Validator Signing Key Leak (Not Smart Contract Vulnerability)
Status: Team Suspended Operations
Executive Summary
Gravity Bridge is a cross-chain protocol connecting Ethereum and Cosmos ecosystems. On May 30, 2026, attackers extracted approximately $5.4 million in digital assets using leaked validator signing keys.
This is the fourth major cross-chain security incident in the first week of June 2026, once again highlighting the fatal risks of centralized signing key management.
Asset Loss Breakdown
| Asset Type | Quantity | Value |
|---|---|---|
| USDC | ~$4,300,000 | $4.3M |
| WETH | 274 tokens | ~$553,000 |
| USDT | ~$434,000 | $434K |
| PAXG | 14.16 tokens | ~$64,000 |
| Total | ~$5,400,000 |
Attack Characteristics Analysis
Key Findings
- Not Smart Contract Vulnerability: On-chain analysts confirmed this was a validator signing key leak, not a contract code issue
- Bridge Operations Suspended: Team has instructed all validators to stop running validators and coordinators
- Staggering TVL Ratio: Pre-incident TVL was approximately $11.5M, with nearly half lost in this incident
Fund Flow Tracking
| Stage | Details |
|---|---|
| Attacker Retention | ~2,102 ETH (~$4.23M) |
| Money Laundering Channels | ChangeNow, Binance |
| Timeline | May 30 attack → June 1 public disclosure |
Cross-Chain Bridge Attack Trends: 2026 Data
According to PeckShield statistics, 2026 has seen 14 major cross-chain bridge attacks with cumulative losses of $340.7M:
| Rank | Project | Amount | Date |
|---|---|---|---|
| 1 | KelpDAO | $293M | April |
| 2 | Drift Protocol | $285M | April |
| 3 | DxSale | $7.3M | June |
| 4 | Gravity Bridge | $5.4M | May |
| 5 | Alephium Bridge | $815K | May |
Gravity Bridge vs Other Bridge Attacks Comparison
| Dimension | Gravity Bridge | Typical Smart Contract Attack |
|---|---|---|
| Vulnerability Type | Key Leak | Code Vulnerability |
| Defense Method | Traditional Security (HSM, MPC) | Formal Verification, Code Audit |
| Responsible Party | Centralized Operator | Smart Contract Code |
| Impact Scope | Controllable (suspend operations) | Difficult to modify after deployment |
Security Warnings
Key Management is the Fatal Weakness of Cross-Chain
Gravity Bridge incident proves:
- MPC/HSM is Not a Silver Bullet: Even with multi-signature schemes, key management processes can still be compromised
- Insufficient Validator Decentralization: "Validator signing keys" suggest relatively centralized signing mechanisms may exist
- TVL and Security Mismatch: $11.5M TVL supporting $5.4M in key assets creates disproportionate risk exposure
User Self-Protection Recommendations
- Be cautious when using bridges where bridge TVL > protocol TVL
- Do not store long-term held assets in bridge contracts
- Monitor protocol validator count and governance structure
Data Sources
- Sina Finance: https://finance.sina.com.cn/stock/usstock/summary/2026-06-01/doc-inhzwpyp8549134.shtml
- Crypto Gazette: https://cryptogazette.com/crypto-bridge-hacks-340-million-2026/
Event Progress
- ✅ Team confirmed key leak (ruled out contract vulnerability)
- ✅ All bridge operations suspended
- ⚠️ Validators have stopped working
- ⚠️ Asset tracking in progress, ChangeNow and Binance may assist with freezing
- ❌ Full incident report not yet published
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