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Reproduced Exploit

HYBUX: A user unstaking through the router forfeits their entire accrued reward (1000 HYBUX): _un

Jan 1970•Other•untagged•3 min read

Chain

Other

Category

untagged

Date

Jan 1970

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.

Loading fork state…

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 63683-c-01-incorrect-reward-calculation-pashov-audit-group-none-hy. Standalone Foundry PoC and full write-up: 63683-c-01-incorrect-reward-calculation-pashov-audit-group-none-hy_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/locked-funds · vuln/reward-accounting

Reproduction: a faithful minimal reproduction of the vulnerable finding — the vulnerable function is reproduced verbatim (marked @>) with faithful minimal doubles; local deploy, no fork.

Root cause#

A user unstaking through the router forfeits their entire accrued reward (1000 HYBUX): _unstakeNFTs claims for msg.sender (the router, which holds no position) then wipes the user's accrual, so the reward is never paid and becomes permanently unrecoverable.

SOLIDITY
    }

    function _unstakeNFTs(address _sender, uint256[] calldata _tokenIds) internal {
        claimRewards(); // @> pays _claimRewards(msg.sender)=router, not the delegated _sender; user's accrued reward is then wiped below
        // clear the user's position and reward checkpoint, and return the NFTs
        rewards[_sender] = 0;

Why it's exploitable here#

A user unstaking through the router forfeits their entire accrued reward (1000 HYBUX): _unstakeNFTs claims for msg.sender (the router, which holds no position) then wipes the user's accrual, so the reward is never paid and becomes permanently unrecoverable.

Attack path#

flowchart TD S0["Public claimRewards entry point"] S1["Claim is credited to msg.sender"] S2["Unstake knows the real owner"] S3["Claim ignores _sender, uses caller"] S4["Correct claim-by-address helper"] H["A user unstaking through the router forfeits their entire accrued rewa"] S0 --> S1 S1 --> S2 S2 --> S3 S3 --> S4 S4 --> H

Marked-line walkthrough (Playground)#

The EVM Playground pins each step to the exact executed source line in 0xce01759b82…:

  1. L113 — Public claimRewards entry point: Setup: claimRewards() is the public claim function, but it always credits msg.sender, ignoring who actually owns the staked position.
  2. L114 — Claim is credited to msg.sender: _claimRewards(msg.sender) pays the immediate caller — fine for a direct user, but wrong when a router forwards the call for someone else.
  3. L117 — Unstake knows the real owner: _unstakeNFTs receives _sender, the true position owner, and should settle rewards to that address before removing the stake.
  4. L118 — Claim ignores _sender, uses caller: Root cause: claimRewards() credits msg.sender (the router, no position) instead of _claimRewards(_sender), so the user's reward is never paid.
  5. L128 — Correct claim-by-address helper: _claimRewards(address) is the version that pays a named owner — the one unstake should have called, passing _sender.
  6. L140 — Staking contract definition: Setup: the NFTStakingFixed staking contract that holds positions and accrues per-user rewards.
  7. L154 — Wire up the router address: Setup: stores the router address; the router forwards user unstakes, which is exactly how msg.sender diverges from the real owner.

PoC#

Registry (Foundry, local deploy — verbatim vulnerable source + harm-asserting test + negative control):

BASH
cd 63683-c-01-incorrect-reward-calculation-pashov-audit-group-none-hy_exp
forge test -vvv

The browser Playground replays the same synthetic opcode-for-opcode and measures the harm: A user unstaking through the router forfeits their entire accrued reward (1000 HYBUX): _unstakeNFTs claims for msg.sender (the router, which. Both gates are green (registry forge test PASS + Playground _verify-poc VERDICT: PASS).

Sources & further analysis#

Reproductions & code

Alerts & third-party analyses

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