Integer Overflow in Klever Split-Royalty Validation Enables Unbounded Token Minting

The Klever blockchain node (klever-go) contains a critical integer overflow vulnerability in its split-royalty validation logic. The system decodes per-entry royalty percentages as uint32 values without individual upper bounds and aggregates them into a uint32 accumulator. By providing two split royalty entries that sum to a value exceeding 2^32, the accumulator wraps around to zero, successfully passing the 100% (10000) validation check.

During royalty payout, the system calculates payments using these massive overflowed values, crediting recipients with KLV far exceeding the original royalty pool. The negative remainder is silently discarded rather than returning an error, allowing the attacker to mint KLV or other assets out of thin air. This vulnerability is not gated by existing guards such as FixMarketBuyOverflow and remains exploitable on current mainnet deployments. Because the minted tokens are credited directly via balance modification rather than tracked mint events, the inflation remains invisible in official supply dashboards, posing a significant risk to the economic integrity of the ecosystem.

Attack Chain

1. Attacker crafts a malicious KDA asset creation transaction using the kloperator tool.
2. The transaction includes two split-royalty recipients, each assigned a percentage value of 21474836.48.
3. The node processes these as raw uint32 values (2147483648), causing the sum to wrap around to 0 in the uint32 accumulator.
4. The CheckValid100Params function incorrectly validates the wrapped sum of 0 as permissible.
5. The attacker initiates a standard asset transfer or market buy, triggering the royalty payout logic.
6. The payout logic retrieves the overflowed 2147483648 percentage, calculating a massive credit for the recipient.
7. The AddToBalance function executes, crediting the recipient's wallet with inflated KLV or asset balances.
8. The system silently ignores the resulting negative remainder, finalizing the unauthorized mint.

Impact

Successful exploitation results in the unbounded inflation of KLV and other assets. Because the inflation is handled via direct balance updates rather than tracked minting processes, the supply metrics appear accurate while the token value is eroded. This can lead to a total loss of economic integrity, affecting all holders within the Klever ecosystem. Any user with sufficient funds for transaction fees can exploit this without requiring administrative privileges.

Recommendation

1. Implement per-entry bounds checking in decodeSplitInfo within core/kapp/builtInFunctions/utils.go to reject any individual percentage exceeding HundredPercent (10000).
2. Modify the validation logic in core/kapp/kda/create.go and core/kapp/kda/trigger.go to use uint64 accumulators to prevent integer wrapping during the summation of royalty percentages.
3. Enforce these changes via a new activation-epoch fork flag to ensure historical blocks remain consistent while preventing future exploitation.