/web3-hunt-zksync-era

name: web3-hunt-zksync-era
description: ZKsync Era (Immunefi) completed hunt — 0 findings after exhaustive 5-session audit. Use as a DEFENSE STUDY — learn what makes a protocol unhuntable, which patterns block all 10 bug classes, and when to abandon a target. Contains architecture breakdown, 25 tested attack vectors, and pre-dive scoring refinements for large L1 bridge protocols.

LIVE HUNT: ZKsync Era — DEFENSE STUDY

0 findings after exhaustive 5-session audit. Learn what makes a protocol unhuntable.

See also: [[Web3 Audit]], [[Methodology]], [[Web3 Bug Classes]], [[Trust Map]], [[Lead Ledger]]

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TARGET PROFILE

| Field | Value | |-------|-------| | Protocol | ZKsync Era (L2 rollup) | | Platform | Immunefi | | TVL | $322M (L2BEAT Total Value Secured) | | Bounty | $100K minimum Critical, $1.1M max | | Codebase | 750K LOC (Solidity + Rust + Yul) | | Audits | OpenZeppelin V29 (June 2025), multiple prior audits | | Version | Protocol V29.4 | | Repo | `github.com/matter-labs/era-contracts` | | Primacy | Primacy of Impact — even out-of-scope assets qualify | | Prior payouts | $50K (ChainLight ZK circuit bug) |

Pre-Dive Scorecard

| Check | Result | Score | |-------|--------|-------| | TVL > $500K | $322M | PASS | | Max payout > $10K | $100K minimum | PASS | | Simple protocol? | 750K LOC, L1↔L2 bridge + ZK + governance | PASS (complex) | | < 500 lines? | 750K LOC | PASS | | **Audit quality** | OpenZeppelin (top-tier) on ALL critical paths | **WARNING** |

> **REFINEMENT**: Pre-dive should weight audit quality MORE for large protocols. > A protocol passing TVL/LOC/payout checks can still be unhuntable if OZ/ToB audited the exact code you'd hunt. > Add "audit firm tier" as a SOFT kill signal for 500K+ LOC protocols.

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ARCHITECTURE (What Makes It Hardened)

L1 Bridge Stack

Bridgehub (router)
  ├── L1AssetRouter (token routing)
  │     ├── L1Nullifier (deposit/withdrawal state)
  │     └── L1NativeTokenVault (token custody)
  ├── ChainTypeManager (chain registration)
  └── ValidatorTimelock (RBAC execution delay)

L2 System Contracts (kernel space 0x8000-0xFFFF)

Bootloader (0x8001) → AccountCodeStorage, NonceHolder, KnownCodeStorage,
ImmutableSimulator, ContractDeployer, L1Messenger (0x8008),
MsgValueSimulator, L2BaseToken (0x800a), SystemContext (0x800b),
BootloaderUtilities, Compressor, ComplexUpgrader

L2 User Space Contracts (0x10000+)

Create2Factory, Bridgehub, AssetRouter, NativeTokenVault, MessageRoot

Diamond Proxy Pattern (EIP-2535)

• All facets (Admin, Executor, Mailbox, Getters) share single `ZKChainStorage` struct
• No storage collision possible between facets
• Function selectors explicitly mapped in DiamondCut

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ALL 25 ATTACK VECTORS TESTED

Critical Path (Vectors 1-8)

| # | Vector | Target | Why It Failed | |---|--------|--------|---------------| | 1 | UnsafeBytes offset miscalculation | L1Nullifier `_parseL2WithdrawalMessage` | All callers pre-validate message length before UnsafeBytes calls | | 2 | Legacy/new boundary double-withdrawal | L1Nullifier | `_isLegacyTxDataHash` try/catch returns false on decode failure; encoding prefix discriminator prevents collision | | 3 | `secondBridgeAddress` return value manipulation | Bridgehub `requestL2TransactionTwoBridges` | `>0xFFFF` check blocks system contracts; L2-side `msg.sender` auth makes crafted returns useless | | 4 | Failed deposit claim wrong amount (legacy encoding) | L1Nullifier `claimFailedDeposit` | Legacy hash uses try/catch; `depositHappened` correctly tracks per-encoding-version | | 5 | V29 interop root forgery | Executor | `addChainBatchRoot` requires `onlyChain + onlyL2`; historical roots verified via Merkle | | 6 | Missing access control on sibling function | All bridge contracts | Every external function has appropriate modifier; checked all 50+ external functions | | 7 | Fee-on-transfer token accounting desync | NativeTokenVault | L1ERC20Bridge: `if (amount != _amount) revert TokensWithFeesNotSupported()` | | 8 | Governance timelock bypass | ValidatorTimelock | 5-role RBAC via AccessControlEnumerable; `block.timestamp >= commitTimestamp + delay` |

Extended Surface (Vectors 9-25)

| # | Vector | Why It Failed | |---|--------|---------------| | 9 | GatewayTransactionFilterer bypass | Era mainnet: `transactionFilterer == address(0)`, not used | | 10 | Precommitment sentinel collision | `_revertBatches` properly resets precommitment; sentinel values don't collide | | 11 | L2→L1 message forgery via `sendToL1` | Anyone can call `sendToL1`, but L1 verifies `sender=0x8008` in log — can't forge system log sender | | 12 | Compressor state diff manipulation | `publishCompressedBytecode` called only from bootloader context | | 13 | Admin privilege escalation | Diamond proxy admin is governance; no facet can self-modify | | 14 | Fee calculation overflow | All fee math uses SafeMath or checked arithmetic | | 15 | Free L2 transaction abuse | `reservedDynamic` field properly handled; bootloader validates gas | | 16 | DataEncoding L1/L2 mismatch | All 10 encode/decode pairs verified consistent across L1↔L2 | | 17 | NTV token registration race | `_ensureTokenRegistered` is idempotent; double registration returns same assetId | | 18 | Asset ID collision | `keccak256(chainId, ntvAddress, tokenAddress)` — no collision possible | | 19 | Beacon proxy CREATE2 collision | Standard CREATE2; address determined by deployer+salt+bytecodeHash | | 20 | Cross-contract reentrancy | Each contract has independent ReentrancyGuard AND follows CEI | | 21 | Address aliasing collision | Bijective mapping (add/subtract offset mod 2^160) | | 22 | Diamond proxy selector clash | Explicit selector mapping in DiamondCut; duplicates would revert | | 23 | Priority tree manipulation | Merkle range proofs; `unprocessedIndex` only moves forward | | 24 | Chain migration state corruption | `forwardedBridgeMint` validates consistency; atomic revert on mismatch | | 25 | Cross-chain mes