CVE-2020-26241: Shallow copy bug in geth
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/gethsecurityrelease/
For more information If you have any questions or comments about this advisory: Open an issue in go-ethereum Email us at security@ethereum.org
Other sources
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.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is CVE-2020-26241?
CVE-2020-26241 is a consensus vulnerability in Go Ethereum (Geth) that can cause a chain-split and make vulnerable nodes reject the canonical chain.
What is the impact of CVE-2020-26241?
The impact of CVE-2020-26241 is a chain-split where vulnerable nodes reject the canonical chain.
How can CVE-2020-26241 be exploited?
An attacker can exploit CVE-2020-26241 by deploying a contract that writes 'X' to an EVM memory location, causing Geth to perform a shallow copy on invocation and potentially causing a chain-split.
What is the affected software for CVE-2020-26241?
The affected software for CVE-2020-26241 is Go Ethereum (Geth) versions 1.9.7 to 1.9.17.
How can I fix CVE-2020-26241?
To fix CVE-2020-26241, update to Geth version 1.9.17 or higher.