CVE-2021-41264: Openzeppelin Contracts

Critical severity, CVSS 9.8. EPSS: 1.5% chance of exploitation in the next 30 days.

OpenZeppelin Contracts is a library for smart contract development. In affected versions upgradeable contracts using `UUPSUpgradeable` may be vulnerable to an attack affecting uninitialized implementation contracts. A fix is included in version 4.3.2 of `@openzeppelin/contracts` and `@openzeppelin/contracts-upgradeable`. For users unable to upgrade; initialize implementation contracts using `UUPSUpgradeable` by invoking the initializer function (usually called `initialize`). An example is provided [in the forum](https://forum.openzeppelin.com/t/security-advisory-initialize-uups-implementation-contracts/15301).

Affected products

• Openzeppelin Contracts: from 4.1.0, before 4.3.2 (fixed in 4.3.2)

Published 2021-11-12. Last modified 2026-06-17.