How severe is CVE-2021-39137?

CVE-2021-39137 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-39137?

CVE-2021-39137 affects the following packages: github.com/ethereum/go-ethereum (Go). Ecosystems affected: Go.

How do I fix CVE-2021-39137?

Update github.com/ethereum/go-ethereum to 1.10.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39137 is resolved across your whole dependency graph.

How do I detect CVE-2021-39137 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/ethereum/go-ethereum, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-39137 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2021-39137 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-39137 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-39137?

CVE-2021-39137 has an EPSS (Exploit Prediction Scoring System) score of 1.3%, placing it in the 70th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-39137?

CVE-2021-39137 is classified as CWE-436 (CWE-436). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-39137 published, and has it been updated?

CVE-2021-39137 was published on August 24, 2021 and was last updated on August 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

HIGH severity

CVE-2021-39137 — go-ethereum

HIGHFix: ethereum/go-ethereum#23381

CVE-2021-39137 is a high-severity (CVSS 7.5) CWE-436 vulnerability in github.com/ethereum/go-ethereum. A fix is available for github.com/ethereum/go-ethereum — see the affected versions and patch details below.

Ethereum Contains Consensus Flaw During Block Processing

Also known asGHSA-9856-9gg9-qcmqGO-2022-0254

Published

Aug 24, 2021

Updated

Aug 7, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs70th percentile — riskier than 70% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-39137 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐹github.com/ethereum/go-ethereum

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Impact

A vulnerability in the Geth EVM could cause a node to reject the canonical chain.

Description

A memory-corruption bug within the EVM can cause a consensus error, where vulnerable nodes obtain a different stateRoot when processing a maliciously crafted transaction. This, in turn, would lead to the chain being split in two forks.

All Geth versions supporting the London hard fork are vulnerable (which predates London), so all users should update.

This bug was exploited on Mainnet at block 13107518, leading to a minority chain split.

Patches

A patch is included in the v1.10.8 release. The exact patch to fix the issue is contained within this commit

Workarounds

No workarounds exist, save to update and/or apply the patch commit.

References.

Post-mortem write-up.

Credits

The bug was found by @guidovranken (working for Sentnl during an audit of the Telos EVM) and reported via [email protected].

For more information

If you have any questions or comments about this advisory:

Open an issue in go-ethereum
Email us at [email protected]

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/ethereum/go-ethereum`	≥ 1.10.0&&< 1.10.8	1.10.8`go get github.com/ethereum/go-ethereum@v1.10.8`

Affected Products

1 product · 1 configurations

Application

go ethereumethereum

≥ 1.10.0 && < 1.10.8

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/ethereum/go-ethereum, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/ethereum/go-ethereum to 1.10.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39137 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact A vulnerability in the Geth EVM could cause a node to reject the canonical chain. ### Description A memory-corruption bug within the EVM can cause a consensus error, where vulnerable nodes obtain a different `stateRoot` when processing a maliciously crafted transaction. This, in turn, would lead to the chain being split in two forks. All Geth versions supporting the London hard fork are vulnerable (which predates London), so all users should update. This bug was exploited on Mainnet at block 13107518, leading to a minority chain split. ### Patches A patch is included in th