Incident Overview
On March 5, 2026, Solv Protocol's BRO (BitcoinReserveOffering) vault suffered a $2.73M exploit when an attacker exploited a double-minting flaw in the mint() function, looping burn, mint operations 22 times to inflate 135 BRO tokens into 567M BRO, then exchanging the inflated balance for 38.0474 SolvBTC. The incident affected fewer than 10 users, with Solv Protocol committing to cover all losses and offering a 10% white hat bounty.
The BRO-SOLV-20MAY2026 contract contained a critical double-minting vulnerability in its mint() function. When users minted BRO by transferring a full ERC-3525 NFT, the doSafeTransferIn function triggered the onERC721Received callback, which minted BRO tokens to the caller. However, the mint() function then minted the same amount again, effectively doubling the tokens received. The attacker exploited this by repeatedly looping burn, mint operations 22 times, converting an initial 135 BRO tokens into 567 million BRO tokens. With the massively inflated balance, the attacker used Solv's exchange contract to swap the fraudulent BRO tokens for 38.0474 SolvBTC (~$2.73M). Security firms HypernativeLabs, SlowMist, and CertiK promptly alerted Solv Protocol, enabling rapid response and containment. The protocol confirmed all other vaults and user funds remained secure and committed to covering losses for affected users.
Blockchain Data Reference
Vulnerable Contract: 0x014e6F6b…006869 (BRO-SOLV-20MAY2026)
Exploit Transaction: 0x44e637c7…7a958d
Exploiter Contact Address: 0x08259F9D…2326A9
Incident Report
Protocol Information
What the Attacker Needed to Succeed
Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.
What Auditors Should Check
If you're auditing a protocol with similar architecture to Solv Protocol, these are the critical security checks that could have prevented this incident (March 2026).
- Verify all logic paths related to Other are guarded by proper access controls and input validation
- Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs
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