{"id":"CVE-2020-26241","aliases":["GHSA-69v6-xc2j-r2jf","GO-2022-0771"],"url":"https://o3.security/vulnerability/CVE-2020-26241","summary":"Shallow copy bug in geth","details":"Go Ethereum, or \"Geth\", is the official Golang implementation of the Ethereum protocol. This is a Consensus vulnerability in Geth before version 1.9.17 which can be used to cause a chain-split where vulnerable nodes reject the canonical chain. Geth's pre-compiled dataCopy (at 0x00...04) contract did a shallow copy on invocation. An attacker could deploy a contract that writes X to an EVM memory region R, then calls 0x00..04 with R as an argument, then overwrites R to Y, and finally invokes the RETURNDATACOPY opcode. When this contract is invoked, a consensus-compliant node would push X on the EVM stack, whereas Geth would push Y. This is fixed in version 1.9.17.","published":"2020-11-25T02:15:11.047Z","modified":"2026-08-07T15:12:15.337192Z","cvss":{"score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Go","name":"github.com/ethereum/go-ethereum","fixedVersion":"1.9.17"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://blog.ethereum.org/2020/11/12/geth_security_release/"},{"type":"ADVISORY","url":"https://github.com/ethereum/go-ethereum/security/advisories/GHSA-69v6-xc2j-r2jf"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T15:12:15.337192Z"}}