Hack history / 2022 / Hack or exploit
Ethereum Alarm Clock
Hack or exploit on Oct 20, 2022 · Reward Logic Flaw
SOURCES AGREE ON DATE AND LOSS · 2 SOURCES
Lost
$260K
dollars at the time
Returned
none listed
as the sources state it
Rank
#1,376
among thefts by dollars lost
What happened
On October 20, 2022, Ethereum Alarm Clock's transaction scheduling protocol was exploited via a gas fee refund calculation vulnerability where the cancel() function calculated refunds too high when given inflated transaction fees, allowing attackers to call cancel with high gas prices and extract approximately 204 ETH (~$260K) in overpaid refunds.
Details
- Date
- Oct 20, 2022
- Kind
- Hack or exploit
- Method
- Reward Logic Flaw
- How in
- Smart contract bug
- Target
- DeFi protocol
- Chains
- Ethereum
Reported by
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Ethereum Foundation 2024 · Hack or exploit · undisclosed
Ethereum Foundation 2023 · Hack or exploit · $9K
Verus-Ethereum Bridge 2026 · Hack or exploit · $11.6M
Prysm consensus client bug causes Ethereum validators to lose over $1 million 2025 · Hack or exploit · $1.2M
Ethereum Foundation 2024 · Hack or exploit · undisclosed
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Cite this page
SwanBluechip, "Ethereum Alarm Clock hack, Oct 20, 2022: $260K lost", Crypto hack history, https://swan-hack-tracker.pages.dev/history/i/ht418e0c5cb4/ (data as of 2026-10-31).