LT never charges the minimum admin fee

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 62011-no-fee-enforcement-in-lt-contract-quantstamp-yield-basis-mar. Standalone Foundry PoC and full write-up: 62011-no-fee-enforcement-in-lt-contract-quantstamp-yield-basis-mar_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/fee-calculation · vuln/defi/fee-manipulation

Key info#

Field	Value
Loss	Fee receiver gets 0. The LP keeps 1000. The 10 percent floor would have taken 100
Vulnerable contract	`LT._adminFee`
Attacker EOA	`0x1111111111111111111111111111111111111111`
Attack contract	`Exploit`
Attack tx	`Exploit.run()`
Chain / block / date	Ethereum model · one block · 2025-07
Compiler	solc 0.8.27, cancun, via IR
Bug class	`min_admin_fee` is never stored, so the fee curve has a zero floor

TL;DR#

The LT admin fee is 1e18 - (1e18 - min_admin_fee) * sqrt(1e36 - staked * 1e36 / supply) / 1e18. Nothing in the deployment writes min_admin_fee, so it stays 0. At a stake ratio of 0 the square root term is 1 and the fee is 0. With the intended 10 percent floor the same point charges 10 percent.

A 1000 token gain is charged while nothing is staked. feePaid is 0. The fee receiver balance is 0. The LP sweeps all 1000. The control sets min_admin_fee to 0.1e18, pays the receiver 100, and leaves the LP 900.

The vulnerable code#

SOLIDITY

uint256 inside = 1e36 - (staked * 1e36) / supply;
uint256 root = _sqrt(inside);
// @> VULN: minAdminFee is never assigned on the real LT, so this floor is 0
return 1e18 - (1e18 - minAdminFee) * root / 1e18;

Root cause#

The curve's lower bound is a storage variable that the constructor never sets.

Preconditions#

min_admin_fee is 0.
The gain is valued while staked is 0 and supply is nonzero, which is the point where the floor is the whole fee.

Attack walkthrough#

Mint a 1000 gain onto LT.
charge with staked 0 and supply 1. The fee is 0, so nothing is transferred.
sweep sends 1000 to the LP. The receiver still has 0.
Control: the floor is 0.1e18. The receiver gets 100. The LP gets 900.

Diagrams#

flowchart TD Gain[LT holds a 1000 gain and nothing is staked] --> Curve[The fee curve reads a zero min_admin_fee] Curve --> Zero[Charged fee is 0] Zero --> Sweep[The LP sweeps all 1000] Sweep --> Floor[A 10 percent floor would have paid the receiver 100]

Impact#

The fee receiver, who is paid for ve holders, loses 100 tokens on this gain. The LP keeps the 1000 instead of 900.

Remediation#

Set min_admin_fee in the LT constructor, and allow governance to update it. 0.1e18 is the 10 percent floor used by the control.

How to reproduce#

BASH

cd evm-hack-registry/62011-no-fee-enforcement-in-lt-contract-quantstamp-yield-basis-mar_exp
forge test -vv

Sources#

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 62011-no-fee-enforcement-in-lt-contract-quantstamp-yield-basis-mar_exp (evm-hack-registry mirror).
AuditVault finding: 62011-no-fee-enforcement-in-lt-contract-quantstamp-yield-basis-mar.

Alerts & third-party analyses

Web3Sec X hacked database: search.
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Solodit incident search: search.

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