A vulnerability in the Nomic Bitcoin bridge allowed an attacker to create unbacked nBTC, leaving Alloyed BTC (allBTC) on Osmosis with a significant collateral shortfall. The exploit affected approximately 39.84 nBTC, equivalent to roughly 36% of allBTC’s backing on Osmosis, according to the incident details disclosed by the ecosystem.
An official Osmosis governance proposal attributes the incident to Nomic’s custom transaction-forwarding mechanism, which allegedly allowed nBTC to be double-spent before fraudulent vouchers were transferred to Osmosis through IBC. Osmosis emphasized that neither its blockchain nor the underlying IBC protocol was compromised, isolating the flaw to Nomic-specific infrastructure.
Osmosis Freezes 22.65 BTC After Exploit
Once the incident was identified, Osmosis validators deployed an emergency upgrade aimed at preventing additional losses. The intervention froze approximately 22.65 BTC at an attacker-controlled address, preserving a substantial portion of the assets associated with the exploit while the community evaluates recovery options.
The remaining damage stems from roughly 17.19 nBTC that had already been exchanged against legitimately backed assets before the freeze. Those transactions created an estimated $3.15 million deficit in allBTC backing, leaving the token temporarily undercollateralized even though part of the attacker’s position remains immobilized.
Osmosis has since paused several Bitcoin-related operations, including allBTC minting and redemption as well as deposits and withdrawals involving nBTC and allBTC. Flows connected to the Nomic bridge remain restricted while developers and governance participants assess the extent of the vulnerability and the appropriate recovery mechanism.
Governance Weighs allBTC Backing Recovery
One proposal under consideration would authorize the use of the 22.65 BTC currently held in the frozen address to help restore allBTC backing. Recovering those assets could materially reduce the deficit, but any intervention remains dependent on governance approval and the legal and technical handling of the frozen funds.
Nomic operates as a Cosmos-based network designed to connect native Bitcoin with the broader interchain ecosystem. The exploit did not result from missing BTC in Nomic’s primary reserve vaults, according to the available incident details. The core failure involved the creation and transfer of unauthorized nBTC representations rather than a direct compromise of the Bitcoin reserves themselves.
That distinction is important because the incident demonstrates how synthetic or bridged assets can become underbacked even when the underlying reserve system remains intact. A flaw in accounting or message-forwarding logic can still introduce fraudulent claims against legitimate liquidity elsewhere in the ecosystem.
allBTC services remain constrained while Osmosis and Nomic investigate the forwarding mechanism and determine how to repair the collateral gap. The next milestones are governance approval for recovery measures, completion of technical audits and confirmation that bridge-related operations can resume without recreating the double-spend vulnerability.