52312 sc low cooldown coalescing bug unintended cooldown extension for prior unstakes

Submitted on Aug 9th 2025 at 19:03:25 UTC by @Ambitious_DyDx for Attackathon | Plume Network

• Report ID: #52312
• Report Type: Smart Contract
• Report severity: Low
• Target: https://github.com/immunefi-team/attackathon-plume-network/blob/main/plume/src/facets/StakingFacet.sol
• Impacts: Temporary freezing of funds for at least 24 hours

Description

Brief/Intro

In StakingFacet.sol, userValidatorCooldowns[user][validatorId] usually stores one {amount, cooldownEndTime} slot. When a user unstakes again for the same validator before that slot matures, _processCooldownLogic (internal function) adds the new amount and overwrites cooldownEndTime = block.timestamp + cooldownInterval. This causes earlier-unstaked funds to be re-locked until the new (later) timestamp — multiple unstakes are not independently timed.

Vulnerability Details

Relevant lines in _processCooldownLogic (lines ~818 - 848) show:

finalNewCooledAmountForSlot = currentCooledAmountInSlot + amount;
cooldownEntrySlot.amount = finalNewCooledAmountForSlot;
cooldownEntrySlot.cooldownEndTime = newCooldownEndTime; // <-- overwrites prior end

• _processCooldownLogic coalesces unstakes into a single slot and always sets a fresh cooldownEndTime when adding to an unmatured slot.
• As a result, _processMaturedCooldowns and _calculateTotalWithdrawableAmount use that single timestamp for maturity checks. Overwriting it hides matured portions until the new end, effectively extending their lock.

Impact Details

• Previously-unstaked funds can be re-locked for up to cooldownInterval when a later unstake occurs.
• High user-impact (funds inaccessible for days), even if not stolen — opportunity cost/trust damage.
• Any user doing repeated unstakes to the same validator before the prior cooldown matures won't be able to withdraw prior unstake amounts on time.

References

• https://github.com/immunefi-team/attackathon-plume-network/blob/main/plume/src/facets/StakingFacet.sol?utm\\_source=immunefi

Proof of Concept

Scenario — initial unstake

• t0: call unstake(validatorId, 100)
• Resulting slot: { amount: 100, cooldownEndTime: t0 + cooldownInterval }

Second unstake before first matures

• t1 = t0 + cooldownInterval - 1: call unstake(validatorId, 50)
• Code sees unmatured slot and adds amount, then sets cooldownEndTime = t1 + cooldownInterval
• Slot becomes { amount: 150, cooldownEndTime: t1 + cooldownInterval }

Expected vs actual withdrawability

• At t = t0 + cooldownInterval + ε, calling withdraw() will not include the original 100 — it remains locked until t1 + cooldownInterval.
• Observables:
  • getUserCooldowns(user) returns a single entry with aggregated amount and the later end.
  • amountWithdrawable(user) at t0 + interval + ε does not include the original 100.

Recommendation

Change storage to allow multiple cooldown entries per (user, validator), and push a new entry on each unstake, so each unstake has its own expiry:

struct CooldownEntry {
    uint256 amount;
    uint256 cooldownEndTime;
}

mapping(address => mapping(uint16 => CooldownEntry[])) userCooldownQueues;

// In _processCooldownLogic():
userCooldownQueues[user][validatorId].push(CooldownEntry({
    amount: amount,
    cooldownEndTime: block.timestamp + cooldownInterval
}));

This preserves independent timing for each unstake (no overwriting of earlier cooldownEndTime).