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Reproduced Exploit

KittenSwap: missing lastMintedPeriod update allows unlimited minting

Jan 1970•Other•untagged•2 min read

Chain

Other

Category

untagged

Date

Jan 1970

Source

DeFiHackLabs

PoC & write-upPoC for your local evm-hack-analyzerDeFiHackLabs 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. Exploit reproduction, trace data, and analysis adapted from DeFiHackLabs by SunWeb3Sec — an open registry of reproduced on-chain exploits. The historical source/toolchain is unavailable; this entry is documentation only and claims no executable Forge PoC. DeFiHackLabs PoC directory: src/test.

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#

updatePeriod() mints the weekly emission when currentPeriod>lastMintedPeriod but never updates lastMintedPeriod, so the condition stays true forever and anyone can mint the emission repeatedly - unlimited Kitten supply (9 extra periods = 1800e18 over-minted).

SOLIDITY
        uint256 currentPeriod = getPeriod();
        if (currentPeriod > lastMintedPeriod) { // @> VULN (this line)

Why it's exploitable here#

updatePeriod() mints the weekly emission when currentPeriod>lastMintedPeriod but never updates lastMintedPeriod, so the condition stays true forever and anyone can mint the emission repeatedly - unlimited Kitten supply (9 extra periods = 1800e18 over-minted).

Attack path#

flowchart TD S0["Vulnerable line"] S1["Step"] S2["Step"] S3["Step"] S4["Step"] H["updatePeriod() mints the weekly emission when currentPeriod>"] 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 0x671d353a77…:

  1. L58 — Vulnerable line: Executes if (currentPeriod > lastMintedPeriod) {
  2. L59 — Step: Executes kitten.mint(rebaseReward, WEEKLY_EMISSION);
  3. L66 — Step: Executes ``
  4. L67 — Step: Executes ``
  5. L69 — Step: Executes ``
  6. L72 — Step: Executes address internal constant REBASE = address(0xBEEF);

PoC#

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

BASH
cd 58206-c-02-lack-of-lastmintedperiod-update-allows-unlimited-mintin_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.
  • 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.