{"id":"CVE-2020-26265","aliases":["GHSA-xw37-57qp-9mm4","GO-2021-0105"],"url":"https://o3.security/vulnerability/CVE-2020-26265","summary":"Consensus flaw during block processing in github.com/ethereum/go-ethereum","details":"### Impact\n\nA consensus-vulnerability in Geth could cause a chain split, where vulnerable versions refuse to accept the canonical chain. \n\n### Description\n\n\nA flaw was repoted at 2020-08-11 by John Youngseok Yang (Software Platform Lab), where a particular sequence of transactions could cause a consensus failure.\n\n- Tx 1:\n  - `sender` invokes `caller`.\n  - `caller` invokes `0xaa`. `0xaa` has 3 wei, does a self-destruct-to-self\n  - `caller` does a  `1 wei` -call to `0xaa`, who thereby has 1 wei (the code in `0xaa` still executed, since the tx is still ongoing, but doesn't redo the selfdestruct, it takes a different path if callvalue is non-zero)\n\n- Tx 2:\n  - `sender` does a 5-wei call to 0xaa. No exec (since no code). \n\nIn geth, the result would be that `0xaa` had `6 wei`, whereas OE reported (correctly) `5` wei. Furthermore, in geth, if the second tx was not executed, the `0xaa` would be destructed, resulting in `0 wei`. Thus obviously wrong. \n\nIt was determined that the root cause was this [commit](https://github.com/ethereum/go-ethereum/commit/223b950944f494a5b4e0957fd9f92c48b09037ad) from [this PR](https://github.com/ethereum/go-ethereum/pull/19953). The semantics of `createObject` was subtly changd, into returning a non-nil object (with `deleted=true`) where it previously did not if the account had been destructed. This return value caused the new object to inherit the old `balance`:\n\n```golang\nfunc (s *StateDB) CreateAccount(addr common.Address) {\n\tnewObj, prev := s.createObject(addr)\n\tif prev != nil {\n\t\tnewObj.setBalance(prev.data.Balance)\n\t}\n}\n```\n\nIt was determined that the minimal possible correct fix was\n\n```diff\n+++ b/core/state/statedb.go\n@@ -589,7 +589,10 @@ func (s *StateDB) createObject(addr common.Address) (newobj, prev *stateObject)\n                s.journal.append(resetObjectChange{prev: prev, prevdestruct: prevdestruct})\n        }\n        s.setStateObject(newobj)\n-       return newobj, prev\n+       if prev != nil && !prev.deleted {\n+               return newobj, prev\n+       }\n+       return newobj, nil\n```\n\n### Patches\n\nSee above. The fix was included in Geth `v1.9.20` \"Paragade\".\n\n### Credits\n\nThe bug was found by @johnyangk and reported via bounty@ethereum.org.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [go-ethereum](https://github.com/ethereum/go-ethereum)\n* Email us at [security@ethereum.org](mailto:security@ethereum.org)","published":"2020-12-11T17:15:12.870Z","modified":"2026-08-07T15:12:16.707352Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Go","name":"github.com/ethereum/go-ethereum","fixedVersion":"1.9.20"}],"fix":{"url":"https://github.com/ethereum/go-ethereum/pull/21080","label":"ethereum/go-ethereum#21080"},"references":[{"type":"ADVISORY","url":"https://github.com/ethereum/go-ethereum/releases/tag/v1.9.20"},{"type":"ADVISORY","url":"https://github.com/ethereum/go-ethereum/security/advisories/GHSA-xw37-57qp-9mm4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2020-26265"},{"type":"WEB","url":"https://github.com/ethereum/go-ethereum/pull/21080"},{"type":"WEB","url":"https://github.com/ethereum/go-ethereum/pull/21409"},{"type":"WEB","url":"https://github.com/ethereum/go-ethereum/commit/87c0ba92136a75db0ab2aba1046d4a9860375d6a"},{"type":"PACKAGE","url":"https://github.com/ethereum/go-ethereum"},{"type":"WEB","url":"https://pkg.go.dev/vuln/GO-2021-0105"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T15:12:16.707352Z"}}