18 THORChain Node Operators Lose About 140 RUNE to Zcash Matching Bug

18 THORChain bonds absorb a ZEC matching bug

Eighteen node operators on THORChain are carrying the cost of a Zcash processing bug, after on-chain data showed roughly 140 THORChain (RUNE) stripped from their bonds in a vault slash. The THORChain (RUNE) price moved 4.3% over the past 24 hours as the protocol worked through the fallout. No user or vault funds were touched: everyone who swapped into or out of Zcash received their assets, and the loss landed entirely on the operators who post RUNE as collateral behind the vaults that settle its atomic swaps. THORChain confirmed the incident in an official post published on Monday, October 19, describing a vault slash triggered by an outbound matching problem in its Zcash integration. The bug sat in how the protocol pairs outbound transactions with destinations: a Zcash TEX address, a destination type that only receives shielded transfers, and its matching transparent address were treated as two separate places rather than one, which broke the pairing logic. When the match failed, the vault took the miss, and the bond behind that vault absorbed it. Trading in native ZEC has been frozen since the incident, and the protocol says it stays paused until the repair ships in the v3.21.0 release. The slash did not destroy value on the user side. Swappers got away unharmed, which is the arrangement doing what it was built to do: operators lock up RUNE as collateral precisely so that a vault failure hits their stake first. In this case the failure was software rather than theft, and the 18 operators whose bonds covered it are the only parties out of pocket. About 140 RUNE across 18 bonds is a modest sum per operator, but the incident lands at a sensitive moment for a network that had just grown its active set from 87 to 103 nodes in September, according to its own State of the Network report.

The repair ships in v3.21.0. Its release notes state that all outbound matching now runs through a single shared destination comparator, which means a Zcash TEX address and the transparent address matching it are treated as going to the same place; ZEC outbounds to TEX addresses are queued as transparent transactions. Once the NU6.3 network upgrade is live, transparent ZEC outbounds switch fleet-wide to v6 signing, a change gated behind a HALTSIGNINGZEC control. Activation is set for block 28,366,100, which THORChain expects around 13:40 UTC on Friday, October 23; the notes call the block height authoritative and the timing inexact. Node operators must run a private binary carrying security patches rather than build from source. ZEC is not the only paused service the release targets. Solana trading stopped after a new type of Solana transaction appeared on that chain, and v3.21 lets it restart. The same release patches the App Layer flaw behind the recent attack on Rujira's FIN contract, reopens limit swaps that had been paused over state bloat, and fixes SwapKit affiliate fee payouts so several integrators can turn THORChain back on. Swaps without memos will be priced dynamically against spam, with registration costing more as memo slots fill, and Mimir lets them back in. Monero is left out of v3.21, with its fixes queued for v3.21.1, which has no date. The timing is awkward for a new integration: the ZEC pool is one of THORChain's newest, and the v3.20 upgrade of August 25, 2026 moved Monero and Zcash closer to activation, with a native ZEC liquidity pool launching in early October. v3.20 also reintroduced support for Solana, Base and BNB. The network reopened on June 23 after a security overhaul of 11 stages that took 39 days, following a $10.7 million exploit in May 2026. v3.21 also brings bond providers streaming yield, letting them send a slice of bond yield straight to their wallets; the feature stays off until Mimir enables it.

Bonds covered the software failure

Read against the protocol's own post-mortem, the incident says more about THORChain's loss-absorption order than about Zcash itself. In a sector where cross-chain bridges have repeatedly drained user funds, this failure pushed the cost onto the 18 bonded operators and left every swapper whole, which is the arrangement working as written. The damage was small in token terms, roughly 140 THORChain (RUNE) spread across 18 bonds, but it arrived days after the active set grew from 87 to 103 nodes, meaning more bonded capital now sits behind each future vault error. Nothing in the protocol's post offers the slashed operators a refund; their path back runs through node earnings, starting with the streaming yield v3.21 puts in their hands.