{"id":"CVE-2025-27105","aliases":["GHSA-4w26-8p97-f4jp","PYSEC-2025-31"],"url":"https://o3.security/vulnerability/CVE-2025-27105","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```","published":"2025-02-21T21:27:28.056Z","modified":"2026-08-12T03:51:08.964131319Z","cvss":null,"epss":{"score":0.0057,"percentile":0.45776,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"vyper","fixedVersion":"0.4.1"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/27xxx/CVE-2025-27105.json"},{"type":"ADVISORY","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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:08.964131319Z"}}