OAK — OnChain Attack Knowledge

Worked example · 2026-10

Argent-style smart wallets — a settable recovery period wrapped the deadline into the past, and a signed payload could be replayed in one transaction — unnamed smart-wallet system / Ethereum — 2026-10-19

Loss
~$59.8K (SlowMist).
OAK Techniques observed
OAK-T9.016 (Contract Accounting-State Invariant Flaw — primary. Two flaws per SlowMist. (1) The recovery module's unrestricted setter 0x254a2e49 accepted a recovery period that made the computed deadline overflow to a past timestamp, so a guardian-signed recovery finalised in the same transaction and changed the wallet owner. (2) The execution module did not reject reuse of an identical signed 0xaacaaf88 payload; it ran 19 times in one transaction and nine in the other, and the attacker traded the repeats around a thin MARK/WETH pool. See techniques/T9.016-contract-accounting-state-invariant-flaw.md).
Attribution
pseudonymous (0xc10609ce5c032db92e562e463b1234aab0872b02).
Key teaching point
Security delays and nonces are invariants, not parameters. A recovery delay anyone can set, and a signature without single-use enforcement, each remove the one property the module exists for.

Summary

SlowMist flagged two Ethereum transactions on 2026-10-19 against wallets 0xe545b9a69bff1bf0ed2e922551dda4afc8ee8f66 and 0x5a79e5772493cf4329682d202aa2d28f85a85440.

Timeline (UTC)

Read it as three stages. Get in: two missing invariants in the wallet modules. Prepare: not published. Take: two Ethereum transactions. Times are from SlowMist's alert.

When What happened OAK
Before 2026-10-19 (undisclosed) The recovery module's setter 0x254a2e49 has no access restriction, and a crafted recovery period makes the computed deadline wrap to a timestamp in the past. Separately, the execution module does not reject reuse of an identical signed 0xaacaaf88 payload. Since when is not published. T9.016
2026-10-19 (preparation undisclosed) Funding of the attacker address and any rehearsal are not published. —
2026-10-19 (time undisclosed) A guardian-signed recovery is finalised in the same transaction it is started, because the deadline is already in the past, and the wallet owner is changed. T9.016
2026-10-19 (time undisclosed) The identical signed payload is executed 19 times in one transaction and nine times in the other. The repeats are used to trade around a low-liquidity MARK/WETH pool. Transactions: 0xbfed8d33561ed5f9cbd0f4e62a5bbd20187a64f3e22180148dcb58ed6ebaa795 and 0xa0ee8f914205a948c79eca039b7d8265537eb220472c9be1455d3321f1bd571b. SlowMist does not say which transaction did which. T9.016
after the transactions (undisclosed) Total loss about $59.8K. Where it went is not published. —
2026-10-19 12:21:40 SlowMist publishes its alert. response
after 2026-10-19 (undisclosed) No operator or wallet-vendor statement appears in the cited sources. The affected system is not named. response

Key addresses:

Root-cause evidence

Public references

Techniques demonstrated (1)