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Reproduced Exploit

Subsequent cross-chain borrow skips accrued interest — AuditVault synthetic reduction

This bug report discusses an issue that was found by a group of individuals on a platform called GitHub. The issue involves borrowing the same asset more than once on a specific chain, which causes the recorded debt to be less than the actual debt. This can result in incorrect calculations of accou…

May 2025•Other•logic•4 min read

Chain

Other

Category

logic

Date

May 2025

Source

AuditVault

PoC & write-upPoC for your local evm-hack-analyzerAuditVault PoCs

EVM Playground

Source-level debugger — step opcodes and Solidity in sync

evm-hack-analyzer

The attack is replayed in an in-browser EVM preloaded with the exact dumped fork state. The execution tree shows every call; step by Solidity line or by opcode across all depths — source, Stack, Memory, Storage, Balances (native / ERC-20 / NFT), Transient storage and Return value stay in sync. Click a tree node, opcode, or source line to jump. No backend, no live RPC.

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Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 58397-h-28-subsequent-crosschain-borrows-dont-accrue-interest-on-e. Standalone Foundry PoC and full write-up: 58397-h-28-subsequent-crosschain-borrows-dont-accrue-interest-on-e_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/state-update · vuln/arithmetic/precision-loss

Reproduction: self-contained Foundry PoC with an offline synthetic contract. Full trace: output.txt.

AuditVault finding: 58397 · H-28: Subsequent Cross‐Chain Borrows don’t Accrue interest on existing principal when borrowing the same Asset

Key info#

ImpactHIGH — Subsequent cross-chain borrow skips accrued interest
ProtocolLEND
FindingAuditVault #58397
Reporthttps://github.com/sherlock-audit/2025-05-lend-audit-contest-judging
SourceAuditVault finding
Compiler^0.8.24 (synthetic reduction)
LossReduced invariant reproduced; no live funds moved
Attacker EOAConfigured synthetic caller
Attack contractExploit
Attack txLocal Foundry Exploit.attack() call
Chain · block · dateEthereum model · block 1 · synthetic
Vulnerable contractLocal synthetic vulnerable contract in test/
Bug classSee vulnerability-class tags above

TL;DR#

This bug report discusses an issue that was found by a group of individuals on a platform called GitHub. The issue involves borrowing the same asset more than once on a specific chain, which causes the recorded debt to be less than the actual debt. This can result in incorrect calculations of account liquidity, allowing the user to borrow more than they should be allowed to. The root cause of this issue is due to a mistake in the code that updates the user's borrowed amount. This bug can be exploited by a user who initiates multiple cross-chain borrows on the same asset with enough time in between. The impact of this bug is that it can potentially lead to an illiquid market. A proof of concept can be provided upon request. To mitigate this issue, the code needs to be modified to account for the accumulated borrow index when updating the existing borrowed amount.

Background#

The upstream report is a Solidity finding. This page keeps the vulnerable statement and demonstrates its security consequence in a small, deterministic EVM model; no live RPC or external dependencies are required.

The vulnerable code#

SOLIDITY
// The exact vulnerable pattern is retained in test/58397-h-28-subsequent-crosschain-borrows-dont-accrue-interest-on-e.sol.
// @> see the marked statement in the synthetic reduction

Root cause#

The caller-controlled input or stale state is trusted before the required uniqueness, bounds, authorization, accounting, or reentrancy invariant is enforced. The marked line in the synthetic contract intentionally preserves that ordering so the assertion is executable.

Preconditions#

  • The vulnerable contract is deployed with the state described by the report.
  • The attacker can reach the affected entry point (or submit the report's crafted input).

Attack walkthrough#

  1. Exploit.run() initializes the minimal state from the report.
  2. The marked vulnerable operation executes without its required check.
  3. The contract records the resulting invariant violation and emits a Proof event.
  4. The test asserts the harm; the passing trace is recorded at output.txt:4.

Diagrams#

flowchart TD A[Attacker supplies crafted input] --> B[Vulnerable operation] B --> C{Missing invariant check} C --> D[Security impact demonstrated]
sequenceDiagram participant A as Attacker participant V as Vulnerable contract participant S as State A->>V: invoke affected entry point V->>S: apply unchecked update S-->>A: harm is observable

Remediation#

Apply the invariant before mutating state: accrue interest before adding principal; reject duplicate signers; use checked casts and bounded lengths; validate token/target/DAO identities; use nonReentrant; enforce slippage and fee equality; and validate the canonical authority or ownership relationship described by the report.

How to reproduce#

BASH
cd evm-hack-registry/58397-h-28-subsequent-crosschain-borrows-dont-accrue-interest-on-e_exp
forge test -vvvvv

The test is offline and uses only the shared forge-std library. The corresponding Playground bundle is generated from scripts/poc-configs/58397-h-28-subsequent-crosschain-borrows-dont-accrue-interest-on-e.mjs.

Sources#

Reference: https://github.com/sherlock-audit/2025-05-lend-audit-contest-judging

Sources & further analysis#

Reproductions & code

Alerts & third-party analyses

  • Web3Sec X hacked database: search.
  • Rekt leaderboard: search.
  • Solodit incident search: search.

These dashboards index community alerts tweets, post-mortems, and independent write-ups. Reach them through the protocol name above to cross-check this reproduction against other analyses.