# Security Alert - Solidity - Variables can be overwritten in storage

DevFeed: [Security Alert - Solidity - Variables can be overwritten in storage](<https://devfeed.tech/articles/security-alert-solidity-variables-can-be-overwritten-in-storage-16786.md>)

Original publisher: [Read original article](<https://blog.ethereum.org/en/2016/11/01/security-alert-solidity-variables-can-overwritten-storage>)

Author: Christian Reitwiessner

Published: 2016-11-01T08:40:44Z

Content type: news

Language: en

Sources: [Ethereum Foundation Blog](<https://devfeed.tech/sources/ethereum-foundation-blog.md>)

Topics: [Solidity](<https://devfeed.tech/topics/solidity.md>), [Security](<https://devfeed.tech/topics/security.md>), [Ethereum](<https://devfeed.tech/topics/ethereum.md>)

Tags: [arrays](<https://devfeed.tech/tags/arrays.md>), [compiler](<https://devfeed.tech/tags/compiler.md>), [ethereum](<https://devfeed.tech/tags/ethereum.md>), [security](<https://devfeed.tech/tags/security.md>)

## AI overview

A Solidity storage-packing vulnerability can allow oversized values in one state variable to overwrite an adjacent variable. The issue affects compiler versions 0.1.6 through 0.4.3, including 0.4.4 pre-releases, and the article recommends recompiling undeployed contracts with Solidity 0.4.4 or later and deactivating, removing funds from, or upgrading deployed contracts.

## Source excerpt

Summary: In some situations, variables can overwrite other variables in storage. Affected Solidity compiler versions: 0.1.6 to 0.4.3 (including 0.4.4 pre-release versions) Detailed description: Storage variables that are smaller than 256 bits are packed together into the same 256 bit slot if they can fit. If a...