CVE-2026-54754

Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.19, marketplace settlement in core/kapp/market/market.go reads MarketOrderData.ReferralPercentage from the listing while reading asset.Royalties.MarketPercentage live at purchase time. An asset owner can create a valid listing and then use AssetTrigger UpdateRoyalties to make the combined referral and royalty percentages exceed the bid. executeBuyMarket pays referral and royalty amounts unconditionally while computeMarketOwnerAmount silently skips a nonpositive seller remainder, allowing MarketBuy, BuyItNow, or auction Claim settlement to credit more KLV or sale currency than the buyer paid. This can create unbacked currency and corrupt token supply integrity. This issue is fixed in version 1.7.19.

Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.19, marketplace settlement in core/kapp/market/market.go reads MarketOrderData.ReferralPercentage from the listing while reading asset.Royalties.MarketPercentage live at purchase time. An asset owner can create a valid listing and then use AssetTrigger UpdateRoyalties to make the combined referral and royalty percentages exceed the bid. executeBuyMarket pays referral and royalty amounts unconditionally while computeMarketOwnerAmount silently skips a nonpositive seller remainder, allowing MarketBuy, BuyItNow, or auction Claim settlement to credit more KLV or sale currency than the buyer paid. This can create unbacked currency and corrupt token supply integrity. This issue is fixed in version 1.7.19.

Summary

When a marketplace order is settled (MarketBuy / BuyItNow, and auction Claim), the buyer's payment is split three ways — referral, royalties, and the seller (market-order owner) remainder:

marketOwnerAmount = CurrentBid − referralAmount − royaltiesAmount

Referral and royalties are paid out unconditionally, but the seller remainder is only paid when positive (computeMarketOwnerAmount returns Ok and pays nothing when the amount is <= 0). When referral% + royalty% exceeds 100% of the bid, marketOwnerAmount goes negative and is silently skipped — so the marketplace pays out more KLV / sale currency than the buyer paid in, minting the difference out of thin air.

The combined ceiling royalty% + referral% <= 100% is checked once, at listing time (Sell). But the two percentages are sourced asymmetrically at settlement:

• referral % is snapshotted into the order at Sell (MarketOrderData.ReferralPercentage);
• royalty % is never snapshotted — it is read live from the asset at buy time (asset.Royalties.MarketPercentage).

So the listing-time invariant is a time-of-check/time-of-use guarantee only. After a valid listing, the asset owner raises the royalty MarketPercentage via AssetTrigger → UpdateRoyalties; at the next buy the live royalty plus the snapshotted referral exceed 100%, and the settlement mints the overflow. The minted funds land in attacker-controlled referral / royalty addresses.

This was actively exploited on mainnet (see Evidence), minting tens of millions of KLV before the emergency guard was deployed.

Affected component

• Repository: klever-io/klever-go (node).
• Settlement / mint site: core/kapp/market/market.go — executeBuyMarket (L575+), computeReferralAmount (L361+), computeRoyaltiesAmount (L490+), computeRoyaltiesFixedDeposit (L443+), computeMarketOwnerAmount (L540+).
• TOCTOU sources: Sell combined check (market.go:908), order snapshot of referral but not royalty (market.go:997), live royalty mutation via core/kapp/kda/trigger.go — handleUpdateRoyaltiesNFTandSFT (L613+, sets asset.Royalties.MarketPercentage at L670).
• Reachable from both Buy (BuyItNow, market.go:204+) and auction Claim (market.go:705, market.go:731).
• Pre-fix: not gated by any fork flag — exploitable on mainnet. The fix is gated behind the new FixMarketBuyOverflow activation-epoch flag.

Root cause

1. Settlement pays referral + royalty unconditionally, seller remainder only if positive

core/kapp/market/market.go — executeBuyMarket (L575+):

referralAmount, _  := tools.ComputePercentageI64(marketOrder.CurrentBid,
                          int64(marketOrder.ReferralPercentage), ...)        // L583: SNAPSHOT referral %
royaltiesAmount, _ := tools.ComputePercentageI64(marketOrder.CurrentBid,
                          int64(asset.Royalties.MarketPercentage), ...)      // L587: LIVE royalty %
marketOwnerAmount := marketOrder.CurrentBid - referralAmount - royaltiesAmount  // L591: can go negative

// ---- FIX (FixMarketBuyOverflow), added by the patch ----
if m.forkController.FixMarketBuyOverflow() && marketOwnerAmount < 0 {         // L593-596
    ctx.Receipts().AddError(ctx.ContractID(), common.ErrFieldInvalidRoyalties, common.ErrInvalidValue.Error())
    return transaction.Transaction_AmountInvalid, common.ErrInvalidValue
}

m.computeReferralAmount(ctx, marketOrder, referralAmount, currencyID)   // pays referral in full
m.computeRoyaltiesFixedDeposit(ctx, marketOrder, asset)                 // pays fixed royalty (KLV)
m.computeRoyaltiesAmount(ctx, marketOrder, asset, currencyID, royaltiesAmount) // pays % royalty in full
m.computeMarketOwnerAmount(ctx, marketOrder, currencyID, marketOwnerAmount)    // <-- skips when <= 0

computeMarketOwnerAmount (L540-542) — the silent skip:

func (m *marketKapp)…

Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.19, marketplace settlement in core/kapp/market/market.go reads MarketOrderData.ReferralPercentage from the listing while reading asset.Royalties.MarketPercentage live at purchase time. An asset owner can create a valid listing and then use AssetTrigger UpdateRoyalties to make the combined referral and royalty percentages exceed the bid. executeBuyMarket pays referral and royalty amounts unconditionally while computeMarketOwnerAmount silently skips a nonpositive seller remainder, allowing MarketBuy, BuyItNow, or auction Claim settlement to credit more KLV or sale currency than the buyer paid. This can create unbacked currency and corrupt token supply integrity. This issue is fixed in version 1.7.19.

Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.19, marketplace settlement in core/kapp/market/market.go reads MarketOrderData.ReferralPercentage from the listing while reading asset.Royalties.MarketPercentage live at purchase time. An asset owner can create a valid listing and then use AssetTrigger UpdateRoyalties to make the combined referral and royalty percentages exceed the bid. executeBuyMarket pays referral and royalty amounts unconditionally while computeMarketOwnerAmount silently skips a nonpositive seller remainder, allowing MarketBuy, BuyItNow, or auction Claim settlement to credit more KLV or sale currency than the buyer paid. This can create unbacked currency and corrupt token supply integrity. This issue is fixed in version 1.7.19.

Summary

When a marketplace order is settled (MarketBuy / BuyItNow, and auction Claim), the buyer's payment is split three ways — referral, royalties, and the seller (market-order owner) remainder:

marketOwnerAmount = CurrentBid − referralAmount − royaltiesAmount

Referral and royalties are paid out unconditionally, but the seller remainder is only paid when positive (computeMarketOwnerAmount returns Ok and pays nothing when the amount is <= 0). When referral% + royalty% exceeds 100% of the bid, marketOwnerAmount goes negative and is silently skipped — so the marketplace pays out more KLV / sale currency than the buyer paid in, minting the difference out of thin air.

The combined ceiling royalty% + referral% <= 100% is checked once, at listing time (Sell). But the two percentages are sourced asymmetrically at settlement:

• referral % is snapshotted into the order at Sell (MarketOrderData.ReferralPercentage);
• royalty % is never snapshotted — it is read live from the asset at buy time (asset.Royalties.MarketPercentage).

So the listing-time invariant is a time-of-check/time-of-use guarantee only. After a valid listing, the asset owner raises the royalty MarketPercentage via AssetTrigger → UpdateRoyalties; at the next buy the live royalty plus the snapshotted referral exceed 100%, and the settlement mints the overflow. The minted funds land in attacker-controlled referral / royalty addresses.

This was actively exploited on mainnet (see Evidence), minting tens of millions of KLV before the emergency guard was deployed.

Affected component

• Repository: klever-io/klever-go (node).
• Settlement / mint site: core/kapp/market/market.go — executeBuyMarket (L575+), computeReferralAmount (L361+), computeRoyaltiesAmount (L490+), computeRoyaltiesFixedDeposit (L443+), computeMarketOwnerAmount (L540+).
• TOCTOU sources: Sell combined check (market.go:908), order snapshot of referral but not royalty (market.go:997), live royalty mutation via core/kapp/kda/trigger.go — handleUpdateRoyaltiesNFTandSFT (L613+, sets asset.Royalties.MarketPercentage at L670).
• Reachable from both Buy (BuyItNow, market.go:204+) and auction Claim (market.go:705, market.go:731).
• Pre-fix: not gated by any fork flag — exploitable on mainnet. The fix is gated behind the new FixMarketBuyOverflow activation-epoch flag.

Root cause

1. Settlement pays referral + royalty unconditionally, seller remainder only if positive

core/kapp/market/market.go — executeBuyMarket (L575+):

referralAmount, _  := tools.ComputePercentageI64(marketOrder.CurrentBid,
                          int64(marketOrder.ReferralPercentage), ...)        // L583: SNAPSHOT referral %
royaltiesAmount, _ := tools.ComputePercentageI64(marketOrder.CurrentBid,
                          int64(asset.Royalties.MarketPercentage), ...)      // L587: LIVE royalty %
marketOwnerAmount := marketOrder.CurrentBid - referralAmount - royaltiesAmount  // L591: can go negative

// ---- FIX (FixMarketBuyOverflow), added by the patch ----
if m.forkController.FixMarketBuyOverflow() && marketOwnerAmount < 0 {         // L593-596
    ctx.Receipts().AddError(ctx.ContractID(), common.ErrFieldInvalidRoyalties, common.ErrInvalidValue.Error())
    return transaction.Transaction_AmountInvalid, common.ErrInvalidValue
}

m.computeReferralAmount(ctx, marketOrder, referralAmount, currencyID)   // pays referral in full
m.computeRoyaltiesFixedDeposit(ctx, marketOrder, asset)                 // pays fixed royalty (KLV)
m.computeRoyaltiesAmount(ctx, marketOrder, asset, currencyID, royaltiesAmount) // pays % royalty in full
m.computeMarketOwnerAmount(ctx, marketOrder, currencyID, marketOwnerAmount)    // <-- skips when <= 0

computeMarketOwnerAmount (L540-542) — the silent skip:

func (m *marketKapp)…