CVE-2020-26241

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.

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.

Shallow copy bug in geth in github.com/ethereum/go-ethereum

### 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 [security@ethereum.org](mailto:security@ethereum.org)

Go Ethereum, o "Geth", es la implementación oficial Golang del protocolo Ethereum. Esta es una vulnerabilidad de Consensus en Geth versiones anteriores a 1.9.17 que puede ser usada para causar una división de cadena donde unos nodos vulnerables rechazan la cadena canónica. El contrato de copia de datos precompilado de Geth (en 0x00 ... 04) hizo una copia superficial en la invocación. Un atacante podría implementar un contrato que escribe X en una región de memoria R de EVM, luego llama a 0x00..04 con R como argumento, luego sobrescribe R en Y y finalmente invoca el código de operación RETURNDATACOPY. Cuando este contrato es invocado, un nodo consensus-compliant empujaría X en la pila de EVM, mientras que Geth empujaría Y. Esto es corregido en la versión 1.9.17