# CVE-2021-41272: SHL, SHR, and SAR operations trigger native exception at key values in besu

> A signed type coercion error in Besu causes native exceptions during specific shift operations, leading to network forks or validator failures.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-7pg2-p5vj-xp5h

## What is CVE-2021-41272?

CVE-2021-41272 is a high-severity denial of service vulnerability in hyperledger besu, published on 13 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Besu is an Ethereum client written in Java. Starting in version 21.10.0, changes in the implementation of the SHL, SHR, and SAR operations resulted in the introduction of a signed type coercion error in values that represent negative values for 32 bit signed integers. Smart contracts that ask for shifts between approximately 2 billion and 4 billion bits (nonsensical but valid values for the operation) will fail to execute and hence fail to validate. In networks where vulnerable versions are mining with other clients or non-vulnerable versions this will result in a fork and the relevant transactions will not be included in the fork. In networks where vulnerable versions are not mining (such as Rinkeby) no fork will result and the validator nodes will stop accepting blocks. In networks where only vulnerable versions are mining the relevant transaction will not be included in any blocks. When the network adds a non-vulnerable version the network will act as in the first case. Besu 21.10.2 contains a patch for this issue. Besu 21.7.4 is not vulnerable and clients can roll back to that version. There is a workaround available: Once a transaction with the relevant shift operations is included in the canonical chain, the only remediation is to make sure all nodes are on non-vulnerable versions.

Weakness: CWE-681 (Incorrect Conversion between Numeric Types)

## Which versions are affected by CVE-2021-41272?

It affects 1 product.


Products: Linuxfoundation Besu.

## How do I fix CVE-2021-41272?

No fix has been published for CVE-2021-41272 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-41272 being exploited?

There is no known exploitation of CVE-2021-41272 in the wild and no public exploit code.

## Other vulnerabilities in hyperledger besu

- [CVE-2022-36025](https://insights.sbomify.com/CVE-2022-36025/): Incorrect Conversion between Numeric Types in Besu Ethereum Client (critical 9.1)
- [CVE-2021-21369](https://insights.sbomify.com/CVE-2021-21369/): Potential DoS in Besu HTTP JSON-RPC API (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-41272 and fix it if it is affected.

What it is: CVE-2021-41272 is a high-severity denial of service vulnerability in hyperledger besu, published on 13 Dec 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-2021-41272 in the wild and no public exploit code.

Affected product: hyperledger besu. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2021-41272/ (Markdown: https://insights.sbomify.com/CVE-2021-41272/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41272
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41272
- OSV: https://osv.dev/vulnerability/CVE-2021-41272

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-41272/
Summaries are generated and may contain mistakes; the official description above is the record.