Splash Patch Stops Cardano StableSwap Exploit but Leaves Millions of ADA Unavailable

Three days after the Splash stable‑swap pool for Cardano‑based ADA/OADA was drained, the technical fix that stopped the exploit has not restored the missing liquidity. Holders of OADA remain unable to exit their positions because the pool lost the ADA needed to facilitate swaps.

Exploit Summary

On September 13, an attacker executed two transactions that removed 2,434,648 ADA and 1,988,222 OADA from the pool. After accounting for the attacker’s 9,870 ADA deposit, the net ADA loss was 2,424,778 before network fees.

Root Cause

The pool’s validator calculated a “tradable” reserve by subtracting accrued protocol fees from its actual balances. The logic failed to enforce that this reserve stay positive, to bound fee changes from both sides, and to require a correct swap direction. These missing checks allowed a transaction to be accepted after the tradable ADA reserve had turned negative.

Patch Limitations

Splash’s code update adds the missing reserve‑domain check (or a two‑sided fee bound), which blocks the documented attack path. However, the patch does not return the ADA that was already withdrawn, nor does it provide a mechanism for OADA holders to redeem their tokens.

Liquidity Gap

Immediately after the drain, the pool held only 10 ADA and about 1.44 million OADA, with a negative tradable ADA reserve and unchanged LP token balances. OADA had no protocol‑level redemption option, and other venues listed in the incident report held only single‑ or double‑digit ADA balances.

Secondary Market Constraints

The attacker’s sale of OADA created additional pressure. At 14:53 UTC on September 13, a Minswap V2 OADA/FLDT pool contained 1,763,923 OADA against 45,751 FLDT, meaning any new ADA/OADA liquidity could be arbitraged against this thin inventory, further limiting effective exits.

Next Steps for Recovery

Restoring a functional pool will require more than corrected validator logic. It will need replenished ADA liquidity or a protocol‑level redemption mechanism for OADA, as well as a strategy to manage the thin OADA inventory in secondary markets.

Current Status of Affected Protocols

Optim Finance announced on September 13 that its protocol was paused, liquidity removed, and OADA‑to‑ADA swaps disabled. An update on September 15 indicated ongoing chain indexing and accounting of impacted addresses, but no restoration of liquidity or redemption was reported.