{"id":"CVE-2023-42460","aliases":["EUVD-2023-0268","GHSA-cx2q-hfxr-rj97","PYSEC-2023-191"],"status":"published","title":"_abi_decode input not validated in complex expressions in Vyper","description":"Vyper is a Pythonic Smart Contract Language for the EVM. The `_abi_decode()` function does not validate input when it is nested in an expression. Uses of `_abi_decode()` can be constructed which allow for bounds checking to be bypassed resulting in incorrect results. This issue has not yet been fixed, but a fix is expected in release `0.3.10`. Users are advised to reference pull request #3626.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00671,"percentile":0.52303,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-682"],"published":"2023-09-26T18:47:09Z","modified":"2026-10-28T02:30:51Z","fixes":[{"ecosystem":"PyPI","package":"vyper","fixed_in":["0.3.10"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"vyper","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.4"},{"fixed":"0.3.10"}]}]},{"source":"osv","ecosystem":"PyPI","package":"vyper","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.4"},{"fixed":"0.3.10"}]}],"versions":["0.3.10rc1","0.3.10rc2","0.3.10rc3","0.3.10rc4","0.3.10rc5","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9"]},{"source":"osv","ecosystem":"PyPI","package":"vyper","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.4"},{"fixed":"0.3.10"}]}],"versions":["0.3.10rc1","0.3.10rc2","0.3.10rc3","0.3.10rc4","0.3.10rc5","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9"]}],"products":[{"vendor":"vyperlang","product":"vyper"}],"references":[{"url":"https://github.com/vyperlang/vyper/security/advisories/GHSA-cx2q-hfxr-rj97","tags":["x_refsource_CONFIRM","x_transferred","Exploit","Patch","Third Party Advisory","advisory","web"]},{"url":"https://github.com/vyperlang/vyper/pull/3626","tags":["x_refsource_MISC","x_transferred","Patch","fix","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-42460","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-191.yaml","tags":["web"]},{"url":"https://github.com/advisories/GHSA-cx2q-hfxr-rj97"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/42xxx/CVE-2023-42460.json","tags":["advisory"]},{"url":"https://github.com/vyperlang/vyper","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2023-42460","title":"_abi_decode input not validated in complex expressions in Vyper","description":"Vyper is a Pythonic Smart Contract Language for the EVM. The `_abi_decode()` function does not validate input when it is nested in an expression. Uses of `_abi_decode()` can be constructed which allow for bounds checking to be bypassed resulting in incorrect results. This issue has not yet been fixed, but a fix is expected in release `0.3.10`. Users are advised to reference pull request #3626.","status":"published","published":"2023-09-26T18:47:09.721Z","modified":"2024-09-24T13:45:05.798Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-682"],"updated_at":"2026-11-02T14:35:18.16233Z"}],"euvd":[{"id":"EUVD-2023-0268","description":"Vyper is a Pythonic Smart Contract Language for the EVM. The `_abi_decode()` function does not validate input when it is nested in an expression. Uses of `_abi_decode()` can be constructed which allow for bounds checking to be bypassed resulting in incorrect results. This issue has not yet been fixed, but a fix is expected in release `0.3.10`. Users are advised to reference pull request #3626.","status":"published","published":"2023-09-26T18:47:09Z","modified":"2024-09-24T13:45:05Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"updated_at":"2026-11-03T00:28:16.146478Z"}],"ghsa":[{"id":"GHSA-cx2q-hfxr-rj97","title":"Vyper's `_abi_decode` input not validated in complex expressions","description":"### Impact\n`_abi_decode()` does not validate input when it is nested in an expression. the following example gets correctly validated (bounds checked):\n```vyper\nx: int128 = _abi_decode(slice(msg.data, 4, 32), int128)\n```\n\nhowever, the following example is not bounds checked\n```vyper\n@external\ndef abi_decode(x: uint256) -\u003e uint256:\n    a: uint256 = convert(_abi_decode(slice(msg.data, 4, 32), (uint8)), uint256) + 1\n    return a  # abi_decode(256) returns: 257\n```\n\nthe issue can be triggered by constructing an example where the output of `_abi_decode` is not internally passed to `make_setter` (an internal codegen routine) or other input validating routine.\n\n### Patches\nhttps://github.com/vyperlang/vyper/pull/3626\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","status":"published","published":"2023-09-26T19:34:53Z","modified":"2024-11-19T17:23:06Z","cvss":[{"version":"4.0","score":6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"medium"},{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-682"],"updated_at":"2026-11-02T14:38:21.777721Z"}],"nvd":[{"id":"CVE-2023-42460","description":"Vyper is a Pythonic Smart Contract Language for the EVM. The `_abi_decode()` function does not validate input when it is nested in an expression. Uses of `_abi_decode()` can be constructed which allow for bounds checking to be bypassed resulting in incorrect results. This issue has not yet been fixed, but a fix is expected in release `0.3.10`. Users are advised to reference pull request #3626.","status":"published","published":"2023-09-27T15:19:32.543Z","modified":"2026-06-17T06:23:52.767Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"primary"}],"cwes":["CWE-682"],"updated_at":"2026-11-02T14:08:31.699785Z"}],"osv":[{"id":"CVE-2023-42460","title":"_abi_decode input not validated in complex expressions in Vyper","description":"Vyper is a Pythonic Smart Contract Language for the EVM. The `_abi_decode()` function does not validate input when it is nested in an expression. Uses of `_abi_decode()` can be constructed which allow for bounds checking to be bypassed resulting in incorrect results. This issue has not yet been fixed, but a fix is expected in release `0.3.10`. Users are advised to reference pull request #3626.","status":"published","published":"2023-09-26T18:47:09.721Z","modified":"2026-10-28T02:30:51.49429618Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-682"],"updated_at":"2026-11-02T15:44:33.792101Z"},{"id":"GHSA-cx2q-hfxr-rj97","title":"Vyper's `_abi_decode` input not validated in complex expressions","description":"### Impact\n`_abi_decode()` does not validate input when it is nested in an expression. the following example gets correctly validated (bounds checked):\n```vyper\nx: int128 = _abi_decode(slice(msg.data, 4, 32), int128)\n```\n\nhowever, the following example is not bounds checked\n```vyper\n@external\ndef abi_decode(x: uint256) -\u003e uint256:\n    a: uint256 = convert(_abi_decode(slice(msg.data, 4, 32), (uint8)), uint256) + 1\n    return a  # abi_decode(256) returns: 257\n```\n\nthe issue can be triggered by constructing an example where the output of `_abi_decode` is not internally passed to `make_setter` (an internal codegen routine) or other input validating routine.\n\n### Patches\nhttps://github.com/vyperlang/vyper/pull/3626\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","status":"published","published":"2023-09-26T19:34:53Z","modified":"2024-11-19T17:33:26.232836Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium"},{"version":"4.0","score":6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-682"],"updated_at":"2026-11-02T15:46:45.639885Z"},{"id":"PYSEC-2023-191","description":"Vyper is a Pythonic Smart Contract Language for the EVM. The `_abi_decode()` function does not validate input when it is nested in an expression. Uses of `_abi_decode()` can be constructed which allow for bounds checking to be bypassed resulting in incorrect results. This issue has not yet been fixed, but a fix is expected in release `0.3.10`. Users are advised to reference pull request #3626.","status":"published","published":"2023-09-27T15:19:00Z","modified":"2023-11-08T04:13:28.966407Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:52:53.837392Z"}]}}