CVE-2020-26242: Denial of service in geth
Impact Denial-of-service (crash) during block processing
Details
Affected versions suffer from a vulnerability which can be exploited through the MULMOD operation, by specifying a modulo of 0: mulmod(a,b,0), causing a panic in the underlying library. The crash was in the uint256 library, where a buffer underflowed.
if d == 0, dLen remains 0
and https://github.com/holiman/uint256/blob/4ce82e695c10ddad57215bdbeafb68b8c5df2c30/uint256.go#L451 will try to access index [-1].
The uint256 library was first merged in this commit, on 2020-06-08. Exploiting this vulnerabilty would cause all vulnerable nodes to drop off the network.
The issue was brought to our attention through a bug report, showing a panic occurring on sync from genesis on the Ropsten network. It was estimated that the least obvious way to fix this would be to merge the fix into uint256, make a new release of that library and then update the geth-dependency.
- https://github.com/holiman/uint256/releases/tag/v1.1.1 was made the same day, - PR to address the issue: https://github.com/holiman/uint256/pull/80 - PR to update geth deps: https://github.com/ethereum/go-ethereum/pull/21368
Patches
Upgrade to v1.9.18 or higher
Workarounds
Not at this time
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. In Geth before version 1.9.18, there is a Denial-of-service (crash) during block processing. This is fixed in 1.9.18.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is CVE-2020-26242?
CVE-2020-26242 is a vulnerability in Go Ethereum (Geth) that allows for a denial-of-service (crash) during block processing.
What version of Go Ethereum is affected by CVE-2020-26242?
Versions of Go Ethereum before 1.9.18 are affected by CVE-2020-26242.
How severe is CVE-2020-26242?
CVE-2020-26242 has a severity level of high, with a CVSS score of 7.5.
How can I fix CVE-2020-26242?
To fix CVE-2020-26242, you need to update to version 1.9.18 or higher of Go Ethereum (Geth).
Where can I find more information about CVE-2020-26242?
You can find more information about CVE-2020-26242 on the Ethereum blog at https://blog.ethereum.org/2020/11/12/geth_security_release/ and on the GitHub page at https://github.com/ethereum/go-ethereum/security/advisories/GHSA-jm5c-rv3w-w83m.