CVE-2021-41264
UUPSUpgradeable vulnerability in OpenZeppelin Contracts
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
UUPSUpgradeable vulnerability in OpenZeppelin Contracts
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.
- Record
CVE-2021-41264- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-665
- Updated
- 2026-11-02
EUVDEUVD-2021-1988
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.
- Record
EUVD-2021-1988- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-5vp3-v4hc-gx76
UUPSUpgradeable vulnerability in @openzeppelin/contracts
Impact
Upgradeable contracts using UUPSUpgradeable may be vulnerable to an attack affecting uninitialized implementation contracts. We will update this advisory with more information soon.
Patches
A fix is included in version 4.3.2 of @openzeppelin/contracts and @openzeppelin/contracts-upgradeable.
Workarounds
Initialize implementation contracts using UUPSUpgradeable by invoking the initializer function (usually called initialize). An example is provided in the forum.
References
For more information
If you have any questions or comments about this advisory, or need assistance executing the mitigation, email us at [email protected].
- Record
GHSA-5vp3-v4hc-gx76- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-665
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2021-41264- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.5 High
AV:N/AC:L/Au:N/C:P/I:P/A:P - Weakness
- CWE-665
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-41264- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-5vp3-v4hc-gx76
UUPSUpgradeable vulnerability in @openzeppelin/contracts
Impact
Upgradeable contracts using UUPSUpgradeable may be vulnerable to an attack affecting uninitialized implementation contracts. We will update this advisory with more information soon.
Patches
A fix is included in version 4.3.2 of @openzeppelin/contracts and @openzeppelin/contracts-upgradeable.
Workarounds
Initialize implementation contracts using UUPSUpgradeable by invoking the initializer function (usually called initialize). An example is provided in the forum.
References
For more information
If you have any questions or comments about this advisory, or need assistance executing the mitigation, email us at [email protected].
- Record
GHSA-5vp3-v4hc-gx76- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-665
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
@openzeppelin/contractsnpm |
4.1.0 up to 4.3.2 | 4.3.2 |
@openzeppelin/contracts-upgradeablenpm |
4.1.0 up to 4.3.2 | 4.3.2 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-41264 is a critical vulnerability (CVSS 9.8) in Openzeppelin Contracts, published September 15, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.49%, the 74th percentile. Fixed in @openzeppelin/contracts 4.3.2.
References
github.com/OpenZeppelin/openzeppelin-contracts/security/advisories/GHSA-5vp3-v4hc-gx76
forum.openzeppelin.com/t/security-advisory-initialize-uups-implementation-contracts/15301
nvd.nist.gov/vuln/detail/CVE-2021-41264