{"id":"CVE-2023-30837","aliases":["GHSA-mgv8-gggw-mrg6","PYSEC-2023-76"],"url":"https://o3.security/vulnerability/CVE-2023-30837","summary":"Vyper storage allocator overflow","details":"### Impact\nThe storage allocator does not guard against allocation overflows. This can result in vulnerabilities like the following:\n```vyper\nowner: public(address)\ntake_up_some_space: public(uint256[10])\nbuffer: public(uint256[max_value(uint256)])\n\n@external\ndef initialize():\n    self.owner = msg.sender\n\n@external\ndef foo(idx: uint256, data: uint256):\n    self.buffer[idx] = data\n```\nPer @toonvanhove, \"An attacker can overwrite the owner variable by calling this contract with calldata: `0x04bc52f8 fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff5 ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff` (spaces inserted for readability)\n`0x04bc52f8` is the selector for `foo(uint256, uint256)`, and the last argument `fff...fff` is the new value for the owner variable.\"\n\n### Patches\npatched in 0bb7203b584e771b23536ba065a6efda457161bb\n\n### Workarounds\n_Is there a way for users to fix or remediate the vulnerability without upgrading?_\n\n### References\n_Are there any links users can visit to find out more?_\n","published":"2023-05-08T16:03:06.162Z","modified":"2026-10-28T02:30:59.332257807Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":{"score":0.00697,"percentile":0.49994,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"PyPI","name":"vyper","fixedVersion":"0.3.8"}],"fix":{"url":"https://github.com/vyperlang/vyper/commit/0bb7203b584e771b23536ba065a6efda457161bb","label":"vyperlang/vyper@0bb7203"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/30xxx/CVE-2023-30837.json"},{"type":"ADVISORY","url":"https://github.com/vyperlang/vyper/security/advisories/GHSA-mgv8-gggw-mrg6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-30837"},{"type":"FIX","url":"https://github.com/vyperlang/vyper/commit/0bb7203b584e771b23536ba065a6efda457161bb"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-76.yaml"},{"type":"PACKAGE","url":"https://github.com/vyperlang/vyper"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:59.332257807Z"}}