Yala YU Stablecoin Depegs from Unauthorized Minting Exploit → Security

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Briefing

The Yala protocol’s Bitcoin-backed YU stablecoin suffered a severe depegging event on September 14, 2025, following an exploit that enabled unauthorized token minting. This breach allowed an attacker to create 120 million unbacked YU tokens on the Polygon network, subsequently bridging and selling 7.71 million of these for $7.7 million in USDC across Ethereum and Solana. The incident caused YU’s value to plummet by 80% from its $1 peg, highlighting critical vulnerabilities in cross-chain smart contract architecture.

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Context

Prior to this incident, the DeFi ecosystem has continuously grappled with the inherent risks of complex smart contract interactions and cross-chain operations, where a single vulnerability can cascade into systemic failures. The Yala protocol, despite its Bitcoin-backed over-collateralization model, operated with an unaddressed flaw in its minting and bridging logic, creating an exploitable attack surface. This class of “infinite mint” vulnerability has historically impacted other cross-chain protocols, underscoring a known risk factor within the decentralized finance landscape.

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Analysis

The attacker leveraged a sophisticated cross-chain bridging vulnerability within Yala’s smart contract architecture, specifically targeting the protocol’s ability to mint YU tokens. By exploiting this flaw, the threat actor was able to mint approximately 120 million YU tokens on the Polygon network without legitimate collateral or authorization. These newly minted, unbacked tokens were then strategically bridged to Ethereum and Solana, where 7.71 million YU were rapidly exchanged for $7.7 million in USDC, creating immense selling pressure. The proceeds were subsequently converted into 1,501 ETH and dispersed across multiple wallets to obfuscate the transaction trail, leading to the YU stablecoin’s dramatic depeg.

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Parameters

Protocol Targeted → Yala (YU Stablecoin)
Attack Vector → Unauthorized Token Minting via Cross-Chain Bridging Vulnerability
Financial Impact → $7.7 Million USDC Stolen; 80% Stablecoin Depeg
Blockchains Affected → Polygon, Ethereum, Solana
Incident Date → September 14, 2025
Remaining Vulnerable Assets → Attacker holds ~112 million YU tokens

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Outlook

In the immediate aftermath, Yala has disabled its Convert and Bridge features and engaged security firms to investigate, though the stablecoin remains depegged. This incident reinforces the critical need for rigorous, multi-faceted smart contract audits and robust cross-chain security mechanisms for all DeFi protocols, especially those involving stablecoin minting. Protocols must implement real-time monitoring for anomalous minting events and ensure sufficient liquidity to absorb market shocks during potential depegs. This exploit will likely drive further scrutiny of Bitcoin-backed stablecoin designs and prompt a re-evaluation of security best practices for bridging solutions, aiming to prevent similar “infinite mint” vulnerabilities from impacting the broader ecosystem.

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Verdict

The Yala YU stablecoin exploit serves as a stark reminder that even collateralized stablecoin models are susceptible to fundamental smart contract and cross-chain vulnerabilities, demanding continuous, advanced security diligence to safeguard digital assets.

Signal Acquired from → coincentral.com