# CVE-2020-26240: Erroneous Proof of Work calculation in geth

> Miners using Geth may erroneously calculate Proof of Work due to a DAG generation flaw, potentially causing chain reorganizations or mining failures.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 Nov 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-v592-xf75-856p, GO-2022-0775

## What is CVE-2020-26240?

CVE-2020-26240 is a medium-severity vulnerability in go-ethereum, published on 25 Nov 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Go Ethereum, or "Geth", is the official Golang implementation of the Ethereum protocol. An ethash mining DAG generation flaw in Geth before version 1.9.24 could cause miners to erroneously calculate PoW in an upcoming epoch (estimated early January, 2021). This happened on the ETC chain on 2020-11-06. This issue is relevant only for miners, non-mining nodes are unaffected. This issue is fixed as of 1.9.24

Weakness: CWE-682 (Incorrect Calculation)

## Which versions are affected by CVE-2020-26240?

3 open source packages ship an affected version, including github.com/ethereum/go-ethereum. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/ethereum/go-ethereum` | Go | All versions | 1.9.24 |
| `github.com/ethereum/go-ethereum` | Go | All versions | 1.9.24 |
| `github.com/ethereum/go-ethereum` | Go | All versions | 1.9.24 |

Products: Ethereum Go Ethereum.

## How do I fix CVE-2020-26240?

Upgrade github.com/ethereum/go-ethereum to 1.9.24 or later.

## Is CVE-2020-26240 being exploited?

There is no known exploitation of CVE-2020-26240 in the wild and no public exploit code.

## Other vulnerabilities in go-ethereum

- [CVE-2026-26314](https://insights.sbomify.com/CVE-2026-26314/): Go Ethereum affected by DoS via malicious p2p message (high 8.7)
- [CVE-2023-42319](https://insights.sbomify.com/CVE-2023-42319/): go-ethereum vulnerable to denial of service via crafted GraphQL query (high 7.5)
- [CVE-2023-40591](https://insights.sbomify.com/CVE-2023-40591/): Denial of service via malicious p2p message in go-ethereum (high 7.5)
- [CVE-2021-42219](https://insights.sbomify.com/CVE-2021-42219/): Denial of service in go-ethereum (high 7.5)
- [CVE-2022-23327](https://insights.sbomify.com/CVE-2022-23327/): Denial of Service in Go-Ethereum (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-26240 and fix it if it is affected.

What it is: CVE-2020-26240 is a medium-severity vulnerability in go-ethereum, published on 25 Nov 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-26240 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/ethereum/go-ethereum (Go): affected all versions; fixed in 1.9.24
- github.com/ethereum/go-ethereum (Go): affected all versions; fixed in 1.9.24
- github.com/ethereum/go-ethereum (Go): affected all versions; fixed in 1.9.24

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2020-26240/ (Markdown: https://insights.sbomify.com/CVE-2020-26240/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-26240
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-26240
- OSV: https://osv.dev/vulnerability/CVE-2020-26240

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-26240/
Summaries are generated and may contain mistakes; the official description above is the record.