HermesVault — Verifier LogicSig Rekey Attack — May 19, 2026

Attacker: 2PYF5VFHZYXR7NDXHEPVNJJ73FKTXKTQ3TAUH6ZIIEEL73MCTXUN4GQEL4 (recipient of the ~261,000 ALGO drained, confirmed verbatim by Giulio Pizzini on 20 May 2026)

Funds moved to: ~261,000 ALGO (~$29,466) drained from HermesVault (app id 2952336704) via rekey of the withdrawal verifier LogicSig. Withdrawal tx: ZBNGF7QOQ6MZZP2PUXPK5VOLZSQBU3QTEYW6UVX4J2JSU2ACEQ7Q. Rekey tx (the exploit): PPYN7EUFUOMGKHJJSZG2DDYMSUIF66LV2YOXMSEJGLVUOYLJCSVQ. 230,000 ALGO (~88%) already refunded; ~30,000 ALGO remaining refundable on request to info@hermesvault.org.

Immutable and permissionless smart contract (no owner, no manager), app id 2952336704 on Algorand mainnet, application account ESJWI..PLN4Y, created by JIKHN..MHFUU on 25 April 2025. Vector: faulty guard in the verifier LogicSig against rekeying. The core zk circuit (Plonk + MiMC via algoplonk) is NOT compromised.

Timeline: On 19 May 2026, the HermesVault exploit hit the Algorand private ZK transactions protocol (app id 2952336704). Vector confirmed verbatim by Giulio Pizzini (lead engineer, Algorand Foundation): 'The vulnerability was a faulty guard in the verifier LogicSig against rekeying. This allowed the attacker to rekey the withdrawal verifier and use it to drain funds, bypassing the zk verification path.' Rekey transaction PPYN7EUFUOMGKHJJSZG2DDYMSUIF66LV2YOXMSEJGLVUOYLJCSVQ executed by the attacker to take control of the withdrawal verifier LogicSig. Then withdrawal transaction ZBNGF7QOQ6MZZP2PUXPK5VOLZSQBU3QTEYW6UVX4J2JSU2ACEQ7Q drained ~261,000 ALGO (~$29,466) to 2PYF5VFHZYXR7NDXHEPVNJJ73FKTXKTQ3TAUH6ZIIEEL73MCTXUN4GQEL4. The core zk circuit (Plonk + MiMC via algoplonk) is NOT compromised. On 20 May 2026 at 01:06 UTC, Pizzini published the complete post-mortem on X with attacker address + 2 txids verbatim. 230,000 ALGO (~88%) already refunded as of disclosure. ~30,000 ALGO remaining refundable on email request to info@hermesvault.org with proof of control of deposit address + secret note. algoplonk has been patched. Deposits disabled, HermesVault retired. ZK is not enough: even with a Zcash-grade Plonk + MiMC circuit, the defense logic surrounding LogicSigs is a critical attack surface.