THORChain Keeps ZEC Swaps Halted After Bug Triggers Vault Slash

ZEC swaps stay frozen after a matching failure

THORChain said on Monday that a bug in how outbound transactions are matched caused a vault slash, and that Zcash (ZEC) swaps will stay halted until a fix ships in its v3.21 upgrade, which is scheduled for around Oct. 23. THORChain is a cross-chain swapping network, meaning it lets users trade assets across different blockchains. Zcash is a cryptocurrency focused on private transactions.

The network said no funds were lost. For users, the practical effect is that ZEC swaps are currently unavailable.

About 140 RUNE taken from 18 node accounts

• Onchain records show roughly 139.93 RUNE deducted from the bonds of 18 node accounts on Oct. 10, based on The Defiant's calculation.
• Those deductions came from bonded capital — RUNE pledged by node operators to help secure the network — rather than from customers' ZEC.
• The figure measures gross deductions in that transaction, not a final net cost after any refunds.
• The trading-halt setting was activated at block 28,181,762 on Oct. 10.
• In the 30 days ending at that halt, the ZEC pool recorded about $190,000 in swap volume, according to Midgard, THORChain's analytics API. That pool-level measure includes internal trade and secured-asset activity, not just native ZEC transfers between wallets.

What THORChain said about the halt

In its update, THORChain said: "An outbound matching issue caused a vault slash. No funds were lost, but trading stays halted until the fix ships in 3.21."

How the pause is set up onchain

THORChain's chain-status endpoint shows ZEC trading paused, and its network settings show ZEC transaction signing disabled. The pause is limited to ZEC: the global trading-pause flag is off.

The technical problem behind the slash

THORChain's technical documentation separates bond slashing, which takes validators' bonded RUNE, from slash points, which cut rewards without touching bonded capital. When an observed outbound payment fails to match an approved instruction, the vault members involved can face a bond penalty.

The Oct. 10 transaction recorded a ZEC payment as a "missing tx out" and charged 18 node accounts. The underlying withdrawal record specified a destination beginning with tex1, while the observed outbound used a t1 address.

The v3.21 release notes describe a shared destination comparator that recognizes equivalence between Zcash TEX and transparent addresses, along with changes to how ZEC payments to TEX addresses are scheduled.

SOL trading, limit swaps and memoless swaps also affected

THORChain said v3.21 contains fixes that allow SOL trading, limit swaps and memoless swaps to be turned back on. The chain-status endpoint also shows SOL trading paused.

When the fix is expected

The release targets block 28,366,100 around Oct. 23, with the block height treated as authoritative and the clock time only an estimate. For ZEC signing, the release notes call for a coordinated upgrade: the signing halt stays in place until every Bifrost instance — the software connecting nodes to external chains — runs the new build.

What is confirmed

THORChain said a matching bug caused a vault slash and that no funds were lost. Onchain records and the network's own endpoints support the halt on ZEC trading and signing, the bond deductions on Oct. 10, and the planned v3.21 upgrade around Oct. 23.

What is still unclear

The exact final cost of the slash is not settled in the available records, because the roughly 139.93 RUNE figure is a gross measure before any refunds. The Oct. 23 date is a target based on a block height, and the release notes say the ZEC signing halt depends on all Bifrost instances running the new build.

Why it matters

THORChain users who want to swap ZEC cannot do so right now. The halt also reaches beyond ZEC, since SOL trading, limit swaps and memoless swaps are affected too. The network says customer funds were not lost, and the penalties fell on node operators' bonded RUNE.

Sources

• The Defiant