# CVE-2021-25835: Authentication bypass by capture-replay in github.com/cosmos/ethermint

> Attackers can replay valid Ethereum transactions on Ethermint due to shared chain ID and signature schemes, enabling unauthorized cross-chain transaction execution.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** Yes
- **Published:** 8 Feb 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-x5f3-qmwj-4f84, GO-2022-0889

## What is CVE-2021-25835?

CVE-2021-25835 is a high-severity vulnerability in n/a, published on 8 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Cosmos Network Ethermint <= v0.4.0 is affected by a cross-chain transaction replay vulnerability in the EVM module. Since ethermint uses the same chainIDEpoch and signature schemes with ethereum for compatibility, a verified signature in ethereum is still valid in ethermint with the same msg content and chainIDEpoch, which enables "cross-chain transaction replay" attack.

Weakness: CWE-294 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2021-25835?

3 open source packages ship an affected version, including github.com/cosmos/ethermint. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/cosmos/ethermint` | Go | All versions | 0.4.1 |
| `github.com/cosmos/ethermint` | Go | All versions | 0.4.1 |
| `github.com/cosmos/ethermint` | Go | All versions | 0.4.1 |

Products: Chainsafe Ethermint.

## How do I fix CVE-2021-25835?

Upgrade github.com/cosmos/ethermint to 0.4.1 or later.

## Is CVE-2021-25835 being exploited?

There is no known exploitation of CVE-2021-25835 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-25834](https://insights.sbomify.com/CVE-2021-25834/): Authentication bypass by capture-replay in github.com/cosmos/ethermint (high 7.5)
- [CVE-2021-25836](https://insights.sbomify.com/CVE-2021-25836/): Business logic in n/a (high 7.5)
- [CVE-2021-25837](https://insights.sbomify.com/CVE-2021-25837/): Business logic in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-25835 and fix it if it is affected.

What it is: CVE-2021-25835 is a high-severity vulnerability in n/a, published on 8 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-25835 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/cosmos/ethermint (Go): affected all versions; fixed in 0.4.1
- github.com/cosmos/ethermint (Go): affected all versions; fixed in 0.4.1
- github.com/cosmos/ethermint (Go): affected all versions; fixed in 0.4.1

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-2021-25835/ (Markdown: https://insights.sbomify.com/CVE-2021-25835/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-25835
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-25835
- OSV: https://osv.dev/vulnerability/CVE-2021-25835

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-25835/
Summaries are generated and may contain mistakes; the official description above is the record.