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CVE-2020-26241

Shallow copy bug in geth

6.5 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
None

Exploit likelihood

1.23%Up 0.6 points since Apr 14, 2021
90%50%10%1%

What each source reports

CVE List Score used 6.5

Shallow copy bug in geth

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.

Record
CVE-2020-26241
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-682
Updated
2026-11-02
EUVDEUVD-2021-1275 6.5

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.

Record
EUVD-2021-1275
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-03
GitHub AdvisoriesGHSA-69v6-xc2j-r2jf 6.5

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/geth_security_release/

For more information

If you have any questions or comments about this advisory:

Record
GHSA-69v6-xc2j-r2jf
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-682
Updated
2026-11-02
NVD 6.5

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.

Record
CVE-2020-26241
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L
CVSS 2.0
5.5 MediumAV:N/AC:L/Au:S/C:N/I:P/A:P
Weakness
CWE-682
Updated
2026-11-02
OSV 7.1

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.

Record
CVE-2020-26241
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L
Updated
2026-11-02
OSVGHSA-69v6-xc2j-r2jf 6.5

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/geth_security_release/

For more information

If you have any questions or comments about this advisory:

Record
GHSA-69v6-xc2j-r2jf
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-682
Updated
2026-11-02
OSVGO-2022-0771 No score

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

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

Record
GO-2022-0771
Updated
2026-11-02
OSVopenSUSE-SU-2025:15424-1 No score

govulncheck-vulndb-0.0.20250807T150727-1.1 on GA media

These are all security issues fixed in the govulncheck-vulndb-0.0.20250807T150727-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2025:15424-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/ethereum/go-ethereum
Go
 1.9.7 up to 1.9.17
1.9.17
govulncheck-vulndb
openSUSE:Tumbleweed
From an advisory covering 44 CVEs
 before 0.0.20250807T150727-1.1
0.0.20250807T150727-1.1

History

History
RecordedChangedSources
affected, facts
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-26241 is a medium vulnerability (CVSS 6.5) in Ethereum Go Ethereum, published November 25, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.23%, the 69th percentile. Fixed in github.com/ethereum/go-ethereum 1.9.17.

References

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