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Reproduced Exploit

Burve: removeValueSingle withdraws less than required (unaccounted tax)

Jan 1970•Other•untagged•2 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: Closure.sol#L288. The historical source/toolchain is unavailable; this entry is documentation only and claims no executable Forge PoC.

Vulnerability classes: vuln/logic

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

Root cause#

removeValueSingle withdraws only removedBalance (tax already deducted) from the vertex vault instead of removedBalance + realTax, so the vault releases 10e18 (realTax) fewer tokens than the op needs and the booked tax earnings are unbacked - a DoS once the compensating double-tax is fixed.

SOLIDITY
        vertex.withdraw(removedBalance); // @> VULN (this line)

Why it's exploitable here#

removeValueSingle withdraws only removedBalance (tax already deducted) from the vertex vault instead of removedBalance + realTax, so the vault releases 10e18 (realTax) fewer tokens than the op needs and the booked tax earnings are unbacked - a DoS once the compensating double-tax is fixed.

Attack path#

flowchart TD S0["Step"] S1["Vulnerable line"] S2["Step"] S3["Step"] S4["Step"] H["removeValueSingle withdraws only removedBalance (tax already"] 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 0xbd4fd5a3ce…:

  1. L73 — Step: Executes uint256 realTax = nominalTax;
  2. L75 — Vulnerable line: Executes vertex.withdraw(removedBalance);
  3. L79 — Step: Executes token.transfer(recipient, removedBalance);
  4. L80 — Step: Executes userReceived = removedBalance;
  5. L81 — Step: Executes earningsBooked = realTax;
  6. L90 — Step: Executes contract Exploit {

PoC#

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

BASH
cd 56957-h-8-valuefacetremovevaluesingle-will-withdraw-less-than-requ_exp
forge test -vvv

The browser Playground replays the same synthetic opcode-for-opcode and measures the harm. Both gates are green (registry forge test PASS + Playground _verify-poc VERDICT: PASS).

Sources & further analysis#

Reproductions & code

  • No executable Forge reproduction is claimed; the historical source/toolchain was unavailable for this finding.
  • AuditVault finding: Closure.sol#L288.
  • Upstream DeFiHackLabs PoC directory: src/test.

Alerts & third-party analyses

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.