CVE-2021-39137Known exploitationPublic exploitNetwork attack vector

Chain split via overlapping RETURNDATA buffer copy

Published Aug 24, 2021 · Updated Aug 4, 2024

Memory corruption in the Geth EVM in go-ethereum 1.10.0 through 1.10.7 allows remote attackers to split the chain via a crafted transaction. During CALL variants, the dataCopy precompile reuses the RETURNDATA backing array, so copying overlapping, shifted slices mutates the source and produces a divergent stateRoot. Any Mainnet node processing the transaction is exposed; affected nodes reject the canonical chain and follow a minority fork.

CVSS severity7.5
High
EPSS probability1.32%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in the Geth EVM in go-ethereum 1.10.0 through 1.10.7 allows remote attackers to split the chain via a crafted transaction. During CALL variants, the dataCopy precompile reuses the RETURNDATA backing array, so copying overlapping, shifted slices mutates the source and produces a divergent stateRoot. Any Mainnet node processing the transaction is exposed; affected nodes reject the canonical chain and follow a minority fork.

The record

CVE
CVE-2021-39137
Published
Aug 24, 2021
Updated
Aug 4, 2024
Vendor
Ethereum Foundation
Product
go-ethereum
Classifications
CWE-436, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 2021Exploitation reportedBSC chain-split exploitation
  3. Aug 27, 2021Exploitation reportedEthereum Mainnet minority chain split
  4. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 1.10.0, < 1.10.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Ethereum Foundation · go-ethereumversion=>= 1.10.0, < 1.10.8

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-436Interpretation Conflict
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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