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Reproduced Exploit

infiniFi: unwinding in the same epoch takes 50 from Bob

balanceOf starts at fromEpoch - 1. A user who already earned the locking reward for epoch 5 can startUnwinding in that epoch and still be counted. The 100 pot is split with Bob.

Mar 2025•Other•logic•2 min read

Chain

Other

Category

logic

Date

Mar 2025

Source

AuditVault

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

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Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 55050-double-claiming-of-accrued-rewards-via-unwinding-after-accru. Standalone Foundry PoC and full write-up: 55050-double-claiming-of-accrued-rewards-via-unwinding-after-accru_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/reward-calculation

Key info#

ProtocolinfiniFi
FindingSpearbit, AuditVault 55050
Vulnerable codeUnwinding.balanceOf
HarmAfter taking 100 on the locking side, the user is also paid 50 of the 100 unwinding pot. Bob receives 50 instead of 100. The fixed balanceOf pays Bob 100.
Chainlocal synthetic

TL;DR#

balanceOf starts at fromEpoch - 1. A user who already earned the locking reward for epoch 5 can startUnwinding in that epoch and still be counted. The 100 pot is split with Bob.

The vulnerable code#

SOLIDITY
        // @> VULN: fromEpoch - 1 includes the arrival epoch
        if (epoch < p.fromEpoch - 1) return 0;

Root cause#

The arrival epoch is included because the loop begins one epoch before fromEpoch. The user was already paid for that epoch on the locking side.

Preconditions#

Bob has been unwinding since epoch 1 with 100 shares. The user was allocated 100 of locking rewards for epoch 5.

Attack walkthrough#

  1. Record the 100 locking allocation. See output.txt.
  2. Seed Bob at epoch 1 and start unwinding in epoch 5.
  3. balanceOf for epoch 5 returns 100 shares.
  4. The 100 pot is split 50 and 50.
  5. The arriving user receives 50.
  6. Bob receives 50. The fixed module excludes the arrival epoch and pays Bob 100.

Diagrams#

flowchart TD A["Locking side already paid 100"] --> B["startUnwinding in epoch 5"] B["startUnwinding in epoch 5"] --> C["Walk begins at epoch 4"] C["Walk begins at epoch 4"] --> D["Pot of 100 is split"] D["Pot of 100 is split"] --> E["Bob receives 50 not 100"]

Impact#

Bob loses 50 of the epoch's unwinding rewards. Skipping the arrival epoch pays him the full 100.

Remediation#

Do not count a position for epochs at or before the epoch in which it started unwinding.

How to reproduce#

BASH
cd 55050-double-claiming-of-accrued-rewards-via-unwinding-after-accru_exp
forge test -vv

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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