CVE-2018-20421

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2018-12-24 · updated 2026-06-17
Weakness: CWE-770

Description

Go Ethereum (aka geth) 1.8.19 allows attackers to cause a denial of service (memory consumption) by rewriting the length of a dynamic array in memory, and then writing data to a single memory location with a large index number, as demonstrated by use of "assembly { mstore }" followed by a "c[0xC800000] = 0xFF" assignment.

Affected products

ethereum go-ethereum: 1.8.19

References

https://github.com/ethereum/go-ethereum/issues/18289
https://github.com/ethereum/go-ethereum/issues/18289

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