# Cycle Balance Underflow Incident Retrospective - Friday, April 1st **URL:** \ **Category:** Developers\ **Created:** [April 4, 2022, 6:45pm UTC](https://forum.dfinity.org/t/cycle-balance-underflow-incident-retrospective-friday-april-1st/11908 "2022-04-04T18:45:59Z")\ **Posts on this page:** 1\ **Showing post:** 4
**Author:** ![goose](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/goose/32/6164_2.png) [@goose](https://forum.dfinity.org/u/goose)\ **Post date:** [June 7, 2022, 7:45am UTC](https://forum.dfinity.org/t/cycle-balance-underflow-incident-retrospective-friday-april-1st/11908/4 "2022-06-07T07:45:56Z")
On April 1st, 2022, at around 14:30, Ceto team was batch deploying a rust version of the NFT trading environment and came across a failure in both deployment and upgrade in one canister. Each trading environment requires 3 canisters deployed, the first few environment setups all succeeded, however, the last one failed to proceed no matter how we tried. Query by the canister ID, dfx canister --network ic status, we found that the canister balance value was close to the maximum status of u64. At that time, I suspected that there was an underflow incident in the cycle balance, and proceeded to restore and upgrade the wallet, but also reported as an error. Therefore, I reported this problem to our community technical exchange group to see how others may fix this issue. In the meantime, I also submitted the incident to Dfinity team via [securitybugs@dfinity.org](mailto:securitybugs@dfinity.org). Paul Liu saw my message in the group and immediately contacted me and worked on resolving the problem. On May 13th, we received the bounty rewards from Dfinity [https://dashboard.internetcomputer.org/transaction/64e1ef167ccd5f21be572f2ce13435daf102563a44759ea30bffbf168d23639f](https://dashboard.internetcomputer.org/transaction/64e1ef167ccd5f21be572f2ce13435daf102563a44759ea30bffbf168d23639f) --- _[View the full topic](https://forum.dfinity.org/t/cycle-balance-underflow-incident-retrospective-friday-april-1st/11908)._