CVE-2020-26241

MEDIUM6.5EPSS 0.30%

Shallow copy bug in geth

Published: 6/29/2021Modified: 3/13/2026

Description

### Impact This is a Consensus vulnerability, 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`, - calls `0x00..04` with `R` as an argument, - 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`. ### Patches No standalone patches have been made. ### Workarounds Upgrade to `1.9.17` or higher. ### References https://blog.ethereum.org/2020/11/12/geth_security_release/ ### For more information If you have any questions or comments about this advisory: * Open an issue in [go-ethereum](https://github.com/ethereum/go-ethereum) * Email us at [[email protected]](mailto:[email protected])

Affected packages (2)

CVSS scores

SourceVersionSeverityVector
osvCVSS 3.1MEDIUM6.5CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

References (5)