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Reproduced Exploit

Caller-supplied ControlTower grants migrator power — AuditVault synthetic reduction

This bug report is about a vulnerability found in a contract called the "2025-08-usg-tangent-judging" contract. The vulnerability was discovered by multiple individuals and can be exploited to drain a victim's collateral to an attacker's account. The root cause of this vulnerability is that the con…

Aug 2025•Other•access-control•4 min read

Chain

Other

Category

access-control

Date

Aug 2025

Source

AuditVault

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

EVM Playground

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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: 63046-h-2-caller-supplied-controltower-lets-anyone-be-the-migrator. Standalone Foundry PoC and full write-up: 63046-h-2-caller-supplied-controltower-lets-anyone-be-the-migrator_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/access-control/missing-auth · vuln/input-validation/missing

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

AuditVault finding: 63046 · H-2: Caller supplied ControlTower lets anyone be the migrator

Key info#

ImpactHIGH — Caller-supplied ControlTower grants migrator power
Protocol[[USG]] - Tangent
FindingAuditVault #63046
Reporthttps://github.com/sherlock-audit/2025-08-usg-tangent-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 is about a vulnerability found in a contract called the "2025-08-usg-tangent-judging" contract. The vulnerability was discovered by multiple individuals and can be exploited to drain a victim's collateral to an attacker's account. The root cause of this vulnerability is that the contract relies on a caller-provided parameter for role checks instead of using its own trusted state. This allows an attacker to pass a fake parameter and gain unauthorized access to the contract's functions. The impact of this vulnerability is significant as it can result in the loss of collateral and debt manipulation for multiple accounts. There are no specific conditions required for this attack to occur, making it a high-risk vulnerability. The report suggests implementing measures to prevent this type of exploit in the future.

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/63046-h-2-caller-supplied-controltower-lets-anyone-be-the-migrator.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/63046-h-2-caller-supplied-controltower-lets-anyone-be-the-migrator_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/63046-h-2-caller-supplied-controltower-lets-anyone-be-the-migrator.mjs.

Sources#

Reference: https://github.com/sherlock-audit/2025-08-usg-tangent-judging

Sources & further analysis#

Reproductions & code

Alerts & third-party analyses

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

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