How severe is CVE-2021-41264?

CVE-2021-41264 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-41264 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-41264?

CVE-2021-41264 affects Openzeppelin Contracts. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-41264?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-41264 published?

CVE-2021-41264 was published on 2021-11-12 and last updated on 2026-06-17.

CVE-2021-41264

CVE-2021-41264 is a critical-severity vulnerability in Openzeppelin Contracts with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-665.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (70th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-665
Affected product: Openzeppelin Contracts
Published: 2021-11-12
Last modified: 2026-06-17

Description

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).

Frequently asked questions

What is CVE-2021-41264?: 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).
How severe is CVE-2021-41264?: CVE-2021-41264 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-41264 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-41264?: CVE-2021-41264 affects Openzeppelin Contracts. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-41264?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-41264 published?: CVE-2021-41264 was published on 2021-11-12 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:openzeppelin:contracts:*:*:*:*:*:node.js:*:*

More vulnerabilities in Openzeppelin Contracts

CVE-2021-39168 — Critical (CVSS 10.0): OpenZepplin is a library for smart contract development. In affected versions a vulnerability in TimelockController…
CVE-2021-39167 — Critical (CVSS 10.0): OpenZepplin is a library for smart contract development. In affected versions a vulnerability in TimelockController…
CVE-2022-35961 — High (CVSS 7.9): OpenZeppelin Contracts is a library for secure smart contract development. The functions `ECDSA.recover` and…
CVE-2022-31198 — High (CVSS 7.5): OpenZeppelin Contracts is a library for secure smart contract development. This issue concerns instances of Governor…
CVE-2022-31172 — High (CVSS 7.5): OpenZeppelin Contracts is a library for smart contract development. Versions 4.1.0 until 4.7.1 are vulnerable to the…
CVE-2022-31170 — High (CVSS 7.5): OpenZeppelin Contracts is a library for smart contract development. Versions 4.0.0 until 4.7.1 are vulnerable to…

All CVEs affecting Openzeppelin Contracts →

Other CWE-665 (Improper Initialization) vulnerabilities

CVE-2021-33635 — Critical (CVSS 9.8): When malicious images are pulled by isula pull, attackers can execute arbitrary code.
CVE-2022-37128 — Critical (CVSS 9.8): In D-Link DIR-816 A2_v1.10CNB04.img the network can be initialized without authentication via /goform/wizard_end.
CVE-2019-10196 — Critical (CVSS 9.8): A flaw was found in http-proxy-agent, prior to version 2.1.0. It was discovered http-proxy-agent passes an auth option…
CVE-2015-8367 — Critical (CVSS 9.8): The phase_one_correct function in Libraw before 0.17.1 allows attackers to cause memory errors and possibly execute…
CVE-2019-14271 — Critical (CVSS 9.8): In Docker 19.03.x before 19.03.1 linked against the GNU C Library (aka glibc), code injection can occur when the…
CVE-2018-11949 — Critical (CVSS 9.8): Failure to initialize the extra buffer can lead to an out of buffer access in WLAN function in Snapdragon Auto,…

Browse all CWE-665 (Improper Initialization) vulnerabilities →