CVE-2021-41272
SHL, SHR, and SAR operations trigger native exception at key values in besu
In short
Besu, an Ethereum client, crashes when processing certain shift operations (SHL, SHR, SAR) with large bit values in smart contracts. This causes the client to reject valid transactions and can split the network into incompatible versions.
Technical detail
A signed integer coercion flaw in Besu versions 21.10.0+ causes SHL, SHR, and SAR operations to throw native exceptions when shift amounts represent negative 32-bit signed integers (~2 billion to 4 billion bits). The vulnerability affects transaction validation and block acceptance, potentially causing network forks or consensus failures depending on the distribution of vulnerable vs. patched nodes.
Summary generated and translated by AI from the 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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
hyperledger · besuWant to know if your infrastructure is exposed to this?
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