{"id":"GHSA-6m97-7527-mh74","summary":"incorrect storage layout for contracts containing large arrays","details":"### Impact\ncontracts containing large arrays might underallocate the number of slots they need. prior to v0.3.8, the calculation to determine how many slots a storage variable needed used `math.ceil(type_.size_in_bytes / 32)`:\n\nhttps://github.com/vyperlang/vyper/blob/6020b8bbf66b062d299d87bc7e4eddc4c9d1c157/vyper/semantics/validation/data_positions.py#L197\n\nthe intermediate floating point step can produce a rounding error if there are enough bits set in the IEEE-754 mantissa. roughly speaking, if `type_.size_in_bytes` is large (\u003e 2**46), and slightly less than a power of 2, the calculation can overestimate how many slots are needed. if `type_.size_in_bytes` is slightly more than a power of 2, the calculation can underestimate how many slots are needed.\n\nthe following two example contracts can result in overwriting of the variable `vulnerable`:\n```vyper\nlarge_array: address[2**64 + 1]  # type_.size_in_bytes == 32 * (2**64 + 1); math.ceil(type_.size_in_bytes / 32) \u003c 2**64 + 1\nvulnerable: uint256\n\n# writing to self.large_array[2**64] will overwrite self.vulnerable\n```\n```vyper\nlarge_dynarray: DynArray[address, 2**64]  # Dynarray has a length word in front, its size in bytes is 32 * (2**64 + 1)\nvulnerable: uint256\n\n# writing to self.large_dynarray[2**64 - 1] will overwrite self.vulnerable\n```\n\nnote that in the latter case, the risk of `vulnerable` being overwritten is relatively small, since it would cost roughly $1.45 million trillion USD at today's gas prices (gas price 20gwei, ETH ~= $1800) in order to extend the DynArray to its full container size.\n\n### Patches\npatched by v0.3.8, specifically in commit https://github.com/vyperlang/vyper/commit/0bb7203b584e771b23536ba065a6efda457161bb.","aliases":["CVE-2023-46247","PYSEC-2023-307"],"modified":"2026-09-10T03:49:59.391185148Z","published":"2023-12-13T13:18:52Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2023-12-13T13:18:52Z","nvd_published_at":"2023-12-13T20:15:49Z","cwe_ids":["CWE-193"],"severity":"HIGH"},"references":[{"type":"WEB","url":"https://github.com/vyperlang/vyper/security/advisories/GHSA-6m97-7527-mh74"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-46247"},{"type":"WEB","url":"https://github.com/vyperlang/vyper/commit/0bb7203b584e771b23536ba065a6efda457161bb"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-307.yaml"},{"type":"PACKAGE","url":"https://github.com/vyperlang/vyper"},{"type":"WEB","url":"https://github.com/vyperlang/vyper/blob/6020b8bbf66b062d299d87bc7e4eddc4c9d1c157/vyper/semantics/validation/data_positions.py#L197"}],"affected":[{"package":{"name":"vyper","ecosystem":"PyPI","purl":"pkg:pypi/vyper"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.3.8"}]}],"versions":["0.1.0b1","0.1.0b10","0.1.0b11","0.1.0b12","0.1.0b13","0.1.0b14","0.1.0b15","0.1.0b16","0.1.0b17","0.1.0b2","0.1.0b3","0.1.0b4","0.1.0b5","0.1.0b6","0.1.0b7","0.1.0b8","0.1.0b9","0.2.1","0.2.10","0.2.11","0.2.12","0.2.13","0.2.14","0.2.15","0.2.16","0.2.2","0.2.3","0.2.4","0.2.5","0.2.6","0.2.7","0.2.8","0.2.9","0.3.0","0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.3.6","0.3.7"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2023/12/GHSA-6m97-7527-mh74/GHSA-6m97-7527-mh74.json","last_known_affected_version_range":"\u003c= 0.3.7"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"}]}