{"id":"CVE-2021-41264","aliases":["EUVD-2021-1988","GHSA-5vp3-v4hc-gx76"],"status":"published","title":"UUPSUpgradeable vulnerability in OpenZeppelin Contracts","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).","severity":{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.01487,"percentile":0.74262,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-665"],"published":"2021-09-15T20:23:17Z","modified":"2026-10-24T10:50:42Z","fixes":[{"ecosystem":"npm","package":"@openzeppelin/contracts","fixed_in":["4.3.2"],"sources":["ghsa","osv"]},{"ecosystem":"npm","package":"@openzeppelin/contracts-upgradeable","fixed_in":["4.3.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"@openzeppelin/contracts","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.1.0"},{"fixed":"4.3.2"}]}]},{"source":"ghsa","ecosystem":"npm","package":"@openzeppelin/contracts-upgradeable","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.1.0"},{"fixed":"4.3.2"}]}]},{"source":"osv","ecosystem":"npm","package":"@openzeppelin/contracts","ranges":[{"type":"SEMVER","events":[{"introduced":"4.1.0"},{"fixed":"4.3.2"}]}]},{"source":"osv","ecosystem":"npm","package":"@openzeppelin/contracts-upgradeable","ranges":[{"type":"SEMVER","events":[{"introduced":"4.1.0"},{"fixed":"4.3.2"}]}]}],"products":[{"vendor":"openzeppelin","product":"contracts"},{"vendor":"openzeppelin","product":"openzeppelin-contracts"}],"references":[{"url":"https://github.com/OpenZeppelin/openzeppelin-contracts/security/advisories/GHSA-5vp3-v4hc-gx76","tags":["x_refsource_CONFIRM","x_transferred","Third Party Advisory","advisory","web"]},{"url":"https://github.com/OpenZeppelin/openzeppelin-contracts/commit/024cc50df478d2e8f78539819749e94d6df60592","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web"]},{"url":"https://forum.openzeppelin.com/t/security-advisory-initialize-uups-implementation-contracts/15301","tags":["x_refsource_MISC","x_transferred","Issue Tracking","Mitigation","Patch","Vendor Advisory","fix","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-41264","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-5vp3-v4hc-gx76"},{"url":"https://github.com/OpenZeppelin/openzeppelin-contracts","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2021-41264","title":"UUPSUpgradeable vulnerability in OpenZeppelin Contracts","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).","status":"published","published":"2021-11-12T17:55:11Z","modified":"2024-08-04T03:08:31.576Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"cna"}],"cwes":["CWE-665"],"updated_at":"2026-11-02T14:32:59.105382Z"}],"euvd":[{"id":"EUVD-2021-1988","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).","status":"published","published":"2021-11-12T17:55:11Z","modified":"2024-08-04T03:08:31Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-03T03:24:18.784846Z"}],"ghsa":[{"id":"GHSA-5vp3-v4hc-gx76","title":"UUPSUpgradeable vulnerability in @openzeppelin/contracts","description":"### Impact\n\nUpgradeable contracts using `UUPSUpgradeable` may be vulnerable to an attack affecting uninitialized implementation contracts. We will update this advisory with more information soon.\n\n### Patches\n\nA fix is included in version 4.3.2 of `@openzeppelin/contracts` and `@openzeppelin/contracts-upgradeable`.\n\n### Workarounds\n\nInitialize 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).\n\n### References\n\n[Post-mortem](https://forum.openzeppelin.com/t/uupsupgradeable-vulnerability-post-mortem/15680).\n\n### For more information\n\nIf you have any questions or comments about this advisory, or need assistance executing the mitigation, email us at security@openzeppelin.com.","status":"published","published":"2021-09-15T20:23:17Z","modified":"2023-01-28T05:02:26Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-665"],"updated_at":"2026-11-02T14:36:23.433782Z"}],"nvd":[{"id":"CVE-2021-41264","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).","status":"published","published":"2021-11-12T18:15:07.733Z","modified":"2026-06-17T04:08:11.91Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"secondary"},{"version":"2.0","score":7.5,"vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","level":"high","assessor":"primary"}],"cwes":["CWE-665"],"updated_at":"2026-11-02T14:07:00.984108Z"}],"osv":[{"id":"CVE-2021-41264","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).","status":"published","published":"2021-11-12T18:15:07.733Z","modified":"2026-10-24T10:50:42.805208418Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:44:21.557945Z"},{"id":"GHSA-5vp3-v4hc-gx76","title":"UUPSUpgradeable vulnerability in @openzeppelin/contracts","description":"### Impact\n\nUpgradeable contracts using `UUPSUpgradeable` may be vulnerable to an attack affecting uninitialized implementation contracts. We will update this advisory with more information soon.\n\n### Patches\n\nA fix is included in version 4.3.2 of `@openzeppelin/contracts` and `@openzeppelin/contracts-upgradeable`.\n\n### Workarounds\n\nInitialize 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).\n\n### References\n\n[Post-mortem](https://forum.openzeppelin.com/t/uupsupgradeable-vulnerability-post-mortem/15680).\n\n### For more information\n\nIf you have any questions or comments about this advisory, or need assistance executing the mitigation, email us at security@openzeppelin.com.","status":"published","published":"2021-09-15T20:23:17Z","modified":"2026-07-08T06:27:43.429315395Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-665"],"updated_at":"2026-11-02T15:46:38.911014Z"}]}}