# Three Cosmos-Based Chains Halted Block Production After a Double-Spend Bug in Shared Code

The defect sits in a module many Cosmos chains inherit, and a fix has been available since a March advisory that not every network applied.

- Published: 2026-08-25T05:50:40.344Z
- Canonical: https://polylog.news/crypto/2026-08-25/three-cosmos-based-chains-halted-block-production-after-a-do
- Publisher: Polylog (Crypto desk)
- Section: crypto
- Sources: [crypto.news](https://crypto.news/cosmos-evm-chains-told-to-halt-after-security-incident/), [Rekt News](https://www.rekt.news/)

Cosmos Labs [urged chains running the Cosmos Ethereum Virtual Machine (EVM) module to halt](https://crypto.news/cosmos-evm-chains-told-to-halt-after-security-incident/) after incidents at MANTRA, TAC and KiiChain, with a detailed report still pending. The three networks stopped producing blocks within days of one another, the strongest available signal that the problem lies in code they share rather than in any one team's contracts.

The underlying defect is in the token-transfer precompile that bridges Cosmos inter-chain transfers into EVM execution. State changes made during recursive calls were not reflected in the outer execution context, which allowed the same token balance to be spent more than once inside a single transaction. That is a classic re-entrancy failure expressed through a state-isolation gap rather than a contract callback. The issue is tracked as advisory [ASA-2026-002](https://github.com/cosmos/evm/security/advisories/GHSA-54gx-3cgr-7mfm), and reporting attributes an [earlier exploitation of the same class against Saga's EVM network in January, for roughly $7 million](https://www.techtimes.com/articles/325233/20260821/mantra-chain-hacked-via-cosmos-evm-bug-that-already-cost-saga-7m-january.htm).

The three incidents differ in impact. MANTRA [halted its mainnet on 21 August](https://thedefiant.io/news/blockchains/mantra-halts-chain-blames-cosmos-evm-module) and restarted about 30 hours later after deploying version 8.4.0, saying the incident touched two chain-managed wallets and not user balances, and blaming an upstream software dependency. TAC said it was investigating an exploited vulnerability on the Cosmos-based EVM side affecting its own token supply and coordinated a validator halt, with its connection to The Open Network offline during the stop. KiiChain said an attacker moved funds out through the Hyperlane bridge onto BNB Smart Chain and halted the network as a precaution. Loss figures for TAC and KiiChain have not been disclosed.

Cosmos Labs identified affected chains earlier this year and coordinated mitigation with several teams, which makes the August cluster look like a patch-adoption problem rather than new attacker research. Shared modules give small chains the security engineering of a large ecosystem only when they actually upgrade. Security publications including [Rekt](https://www.rekt.news/) have documented the same pattern repeatedly across bridge and validator infrastructure.

## What this means

Chains that inherit a common framework also inherit its vulnerabilities, and the gap between advisory publication and validator upgrade is where losses happen. Holders of tokens on small application chains are exposed to a governance and operations risk they cannot inspect, because a halt freezes transfers, staking and bridges at once, and the token price moves while withdrawal is impossible. The direct beneficiaries of that dynamic are the largest chains, where upgrade coordination is professionalized and capital does not need to trust a fifteen-validator restart.

## What to watch

- Whether Cosmos Labs publishes a chain-by-chain patch status, which would show how many networks still run vulnerable code today.
- Whether TAC and KiiChain disclose loss amounts and whether any funds moved to BNB Smart Chain are frozen by exchanges, the practical test of whether cross-chain theft is now recoverable.
- Whether the incidents push application-specific chains to adopt automated upgrade enforcement, or instead accelerate migration of assets back to larger settlement layers.