KittenSwap: gauge deactivation destroys accrued rewards

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: KittenSwap-security-review_2025-05-07. 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#

Voter.killGauge sets claimable[_gauge]=0, permanently destroying a gauge's already-accrued rewards; because _updateFor already advanced supplyIndex[_gauge] to the global index, reviveGauge cannot re-accrue them. Two equally-weighted gauges each accrue 100e18; killing then reviving gauge A makes it receive 0 on distribution while identical gauge B receives its full 100e18, and the equivalent base tokens are stranded in the Voter forever.

SOLIDITY

        require(msg.sender == emergencyCouncil, "not emergency council");
        require(isAlive[_gauge], "gauge already dead");
        isAlive[_gauge] = false;
        claimable[_gauge] = 0; // @> VULN (this line)

Why it's exploitable here#

Attack path#

flowchart TD S0["Setup: gauge alive flag"] S1["Reward accrual routine"] S2["Gauge reward index read"] S3["Distribute pays accrued rewards"] S4["killGauge zeroes accrued rewards"] H["Voter.killGauge sets claimable'_gauge'=0, permanently destro"] 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…:

L93 — Setup: gauge alive flag: Setup: the Voter tracks whether each gauge is active in isAlive, which gates reward distribution.
L143 — Reward accrual routine: _updateFor advances a gauge's accrued rewards up to the global index whenever emissions are notified.
L147 — Gauge reward index read: The gauge's stored supplyIndex is loaded; its delta to the global index becomes newly claimable rewards.
L165 — Distribute pays accrued rewards: distribute settles a gauge's claimable rewards, but killGauge can intervene before it runs.
L180 — killGauge zeroes accrued rewards: Root cause: killGauge sets claimable[_gauge] = 0, discarding rewards the gauge had already accrued.
L185 — reviveGauge cannot restore them: reviveGauge re-enables the gauge, but supplyIndex is already at the global index, so the zeroed rewards can never re-accrue.
L200 — Revived gauge distributes zero: Distribution moves base tokens with a real transfer, yet the revived gauge now pays 0 while its stranded rewards stay in the Voter.

PoC#

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

BASH

cd 58153-h-02-loss-of-claimable-rewards-upon-gauge-deactivation-pasho_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: KittenSwap-security-review_2025-05-07.
Upstream DeFiHackLabs PoC directory: src/test.

Alerts & third-party analyses

DeFiHackLabs incident explorer: search "KittenSwap: gauge deactivation destroys accrued rewards".
Web3Sec X hacked database: search.
Rekt leaderboard: search.
Solodit incident search: search.

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.

Source-level debugger — step opcodes and Solidity in sync