Summary
UUPSUpgradeable vulnerability in @openzeppelin/contracts
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].
Impact
Upgradeable contracts using UUPSUpgradeable may be vulnerable to an attack affecting uninitialized implementation contracts. We will update this advisory with more information soon.
CVE-2021-41264 has a CVSS score of 9.8 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.3.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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A fix is included in version 4.3.2 of @openzeppelin/contracts and @openzeppelin/contracts-upgradeable.
Frequently Asked Questions
- What is CVE-2021-41264? CVE-2021-41264 is a critical-severity security vulnerability in @openzeppelin/contracts (npm), affecting versions >= 4.1.0, < 4.3.2. It is fixed in 4.3.2.
- How severe is CVE-2021-41264? CVE-2021-41264 has a CVSS score of 9.8 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2021-41264?
@openzeppelin/contracts(npm) (versions >= 4.1.0, < 4.3.2)@openzeppelin/contracts-upgradeable(npm) (versions >= 4.1.0, < 4.3.2)
- Is there a fix for CVE-2021-41264? Yes. CVE-2021-41264 is fixed in 4.3.2. Upgrade to this version or later.
- Is CVE-2021-41264 exploitable, and should I be worried? Whether CVE-2021-41264 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-41264 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-41264?
- Upgrade
@openzeppelin/contractsto 4.3.2 or later - Upgrade
@openzeppelin/contracts-upgradeableto 4.3.2 or later
- Upgrade