{"id":"GHSA-4w26-8p97-f4jp","summary":"AugAssign evaluation order causing OOB write within the object in Vyper","details":"Vyper handles AugAssign statements by first caching the target location to avoid double evaluation. However, in the case when target is an access to a DynArray and the rhs modifies the array, the cached target will evaluate first, and the bounds check will not be re-evaluated during the write portion of the statement. In other words, the following code\n\n```vyper\ndef poc():\n    a: DynArray[uint256, 2] = [1, 2]\n    a[1] += a.pop()\n```\n\nis equivalent to:\n```vyper\ndef poc():\n    a: DynArray[uint256, 2] = [1, 2]\n    a[1] += a[len(a) - 1]\n    a.pop()\n```\nrather than:\n```vyper\ndef poc():\n    a: DynArray[uint256, 2] = [1, 2]\n    s: uint256 = a[1]\n    t: uint256 = a.pop()\n    a[1] = s + t  # reverts due to oob access\n```","aliases":["CVE-2025-27105","PYSEC-2025-31"],"modified":"2025-04-09T20:36:40.722370Z","published":"2025-02-21T22:43:33Z","database_specific":{"severity":"LOW","github_reviewed":true,"github_reviewed_at":"2025-02-21T22:43:33Z","nvd_published_at":"2025-02-21T22:15:13Z","cwe_ids":["CWE-787"]},"references":[{"type":"WEB","url":"https://github.com/vyperlang/vyper/security/advisories/GHSA-4w26-8p97-f4jp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-27105"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2025-31.yaml"},{"type":"PACKAGE","url":"https://github.com/vyperlang/vyper"}],"affected":[{"package":{"name":"vyper","ecosystem":"PyPI","purl":"pkg:pypi/vyper"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.4.1"}]}],"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","0.3.10","0.3.10rc1","0.3.10rc2","0.3.10rc3","0.3.10rc4","0.3.10rc5","0.3.2","0.3.3","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9","0.4.0","0.4.0b1","0.4.0b2","0.4.0b3","0.4.0b4","0.4.0b5","0.4.0b6","0.4.0rc1","0.4.0rc2","0.4.0rc3","0.4.0rc4","0.4.0rc5","0.4.0rc6","0.4.1b1","0.4.1b2","0.4.1b3","0.4.1b4","0.4.1rc1","0.4.1rc2","0.4.1rc3"],"database_specific":{"last_known_affected_version_range":"\u003c= 0.4.0","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2025/02/GHSA-4w26-8p97-f4jp/GHSA-4w26-8p97-f4jp.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N"}]}