DIA Lumina: a claim floors the partial day and moves the clock

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 57923-reward-accumulation-manipulation-through-frequent-claims-mix. Standalone Foundry PoC and full write-up: 57923-reward-accumulation-manipulation-through-frequent-claims-mix_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/reward-calculation · vuln/arithmetic/precision-loss · vuln/logic/state-update

Key info#


Protocol	DIA Lumina staking
Finding	MixBytes, AuditVault 57923
Vulnerable code	`Staking._updateRewardAccumulator`
Harm	A stake open for 1.5 days is paid 100. The fair accrual is 150. The second claim in the same block pays 0. The burned amount is 50
Chain	local synthetic

TL;DR#

daysElapsed is (block.timestamp - rewardLastUpdateTime) / 1 days. A gap of 1 day and 12 hours floors to 1, so the accumulator adds one daily rate of 100. The function then sets rewardLastUpdateTime = block.timestamp, which deletes the 12 hours. A second claim sees a gap of 0 and pays 0. The recommended precision formula, timeElapsed = gap * 1e18 / 1 days, pays 150 for the same gap. The control pays that 150.

The vulnerable code#

SOLIDITY

uint256 daysElapsed = (block.timestamp - rewardLastUpdateTime) / SECONDS_IN_A_DAY;
daysElapsedStored = daysElapsed;
rewardAccumulator += RATE * daysElapsed;
// @> VULN: the clock jumps to now even when the division dropped a partial day
this.commitClock(block.timestamp);

commitClock writes rewardLastUpdateTime = nextClock with nextClock equal to block.timestamp.

The fix advances the clock by SECONDS_IN_A_DAY * daysElapsed only, or scales the elapsed time by 1e18 before dividing.

Root cause#

Integer division drops every fraction of a day, and the clock is still moved to the current timestamp. The dropped fraction is not waiting in the gap for the next claim. Calling claim often, including twice at the same timestamp after a fractional day, keeps the floored total and never restores the remainder.

Preconditions#

The daily rate is 100 ether per 10000 of principal, and the stake's principal is 10000. The reward clock is block.timestamp minus 1 day and 12 hours. That gap is computed inside run(). run() does not warp. The staking contract holds 150 ether so the fair amount is funded. The Foundry test warps once before run(), to the same effect as the playground's fixed block timestamp.

Attack walkthrough#

The stake is opened with snapshot 0 and a clock 1.5 days behind the block.
The first claim floors the gap to 1 day, adds 100 to the accumulator, and sets the clock to now.
The staker is paid 100 * 10000 / 10000 = 100.
fairReward uses the unfloored gap and returns 150.
The second claim divides a zero gap, adds nothing, and pays 0.
The staker's balance is 100. burned is 50.

The control multiplies the 1.5 day gap by the rate with 1e18 precision and transfers 150.

Diagrams#

flowchart TD A["Reward clock is 1.5 days behind the block"] --> B["daysElapsed divides by 1 day and floors to 1"] B --> C["VULN: rewardLastUpdateTime is set to now"] C --> D["First claim pays 100"] D --> E["Second claim sees 0 days and pays 0"] E --> F["Fair precision accrual is 150"] F --> G["50 is burned, and the control pays 150"]

Impact#

The staker receives 100 for 1.5 days of a 100-per-day rate. The other 50 never accrues, because the clock no longer covers it. Repeating the claim does not recover it. Every stake that shares this accumulator loses the same floored remainder.

How to reproduce#

BASH

cd 57923-reward-accumulation-manipulation-through-frequent-claims-mix_exp
forge test -vv

run() does not warp. The control test pays 150.

Sources#

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 57923-reward-accumulation-manipulation-through-frequent-claims-mix_exp (evm-hack-registry mirror).
AuditVault finding: 57923-reward-accumulation-manipulation-through-frequent-claims-mix.

Alerts & third-party analyses

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Solodit incident search: search.

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