{"id":"CVE-2023-30629","aliases":["EUVD-2023-0263","GHSA-w9g2-3w7p-72g9","PYSEC-2023-131"],"status":"published","title":"Vyper's raw_call with outsize=0 and revert_on_failure=False returns incorrect success value","description":"Vyper is a Pythonic Smart Contract Language for the ethereum virtual machine. In versions 0.3.1 through 0.3.7, the Vyper compiler generates the wrong bytecode. Any contract that uses the `raw_call` with `revert_on_failure=False` and `max_outsize=0` receives the wrong response from `raw_call`. Depending on the memory garbage, the result can be either `True` or `False`. A patch is available and, as of time of publication, anticipated to be part of Vyper 0.3.8. As a workaround, one may always put  `max_outsize\u003e0`.","severity":{"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":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00883,"percentile":0.59668,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-670"],"published":"2023-04-24T21:58:00Z","modified":"2026-10-28T02:30:34Z","fixes":[{"ecosystem":"PyPI","package":"vyper","fixed_in":["0.3.8"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"vyper","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.1"},{"fixed":"0.3.8"}]}]},{"source":"osv","ecosystem":"PyPI","package":"vyper","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.1"},{"fixed":"0.3.8"}]}],"versions":["0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.3.6","0.3.7"]},{"source":"osv","ecosystem":"PyPI","package":"vyper","ranges":[{"type":"GIT","events":[{"introduced":"0"},{"fixed":"851f7a1b3aa2a36fd041e3d0ed38f9355a58c8ae"}]},{"type":"ECOSYSTEM","events":[{"introduced":"0.3.1"},{"fixed":"0.3.8"}]}],"versions":["0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.3.6","0.3.7"]}],"products":[{"vendor":"vyperlang","product":"vyper"}],"references":[{"url":"https://github.com/vyperlang/vyper/security/advisories/GHSA-w9g2-3w7p-72g9","tags":["x_refsource_CONFIRM","x_transferred","Exploit","Vendor Advisory","advisory","web"]},{"url":"https://github.com/lidofinance/gate-seals/pull/5/files","tags":["x_refsource_MISC","x_transferred","Patch","web","fix"]},{"url":"https://github.com/vyperlang/vyper/commit/851f7a1b3aa2a36fd041e3d0ed38f9355a58c8ae","tags":["x_refsource_MISC","x_transferred","Patch","fix","web"]},{"url":"https://docs.vyperlang.org/en/v0.3.7/built-in-functions.html#raw_call","tags":["x_refsource_MISC","x_transferred","Product","web"]},{"url":"https://github.com/lidofinance/gate-seals/blob/051593e74df01a4131c485b4fda52e691cd4b7d8/contracts/GateSeal.vy#L164","tags":["x_refsource_MISC","x_transferred","Product","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-30629","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-131.yaml","tags":["web"]},{"url":"https://github.com/advisories/GHSA-w9g2-3w7p-72g9"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/30xxx/CVE-2023-30629.json","tags":["advisory"]},{"url":"https://github.com/vyperlang/vyper","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2023-30629","title":"Vyper's raw_call with outsize=0 and revert_on_failure=False returns incorrect success value","description":"Vyper is a Pythonic Smart Contract Language for the ethereum virtual machine. In versions 0.3.1 through 0.3.7, the Vyper compiler generates the wrong bytecode. Any contract that uses the `raw_call` with `revert_on_failure=False` and `max_outsize=0` receives the wrong response from `raw_call`. Depending on the memory garbage, the result can be either `True` or `False`. A patch is available and, as of time of publication, anticipated to be part of Vyper 0.3.8. As a workaround, one may always put  `max_outsize\u003e0`.","status":"published","published":"2023-04-24T21:58:00.227Z","modified":"2025-02-12T16:35:42.775Z","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","assessor":"cna"}],"cwes":["CWE-670"],"updated_at":"2026-11-02T14:35:22.309324Z"}],"euvd":[{"id":"EUVD-2023-0263","description":"Vyper is a Pythonic Smart Contract Language for the ethereum virtual machine. In versions 0.3.1 through 0.3.7, the Vyper compiler generates the wrong bytecode. Any contract that uses the `raw_call` with `revert_on_failure=False` and `max_outsize=0` receives the wrong response from `raw_call`. Depending on the memory garbage, the result can be either `True` or `False`. A patch is available and, as of time of publication, anticipated to be part of Vyper 0.3.8. As a workaround, one may always put  `max_outsize\u003e0`.","status":"published","published":"2023-04-24T21:58:00Z","modified":"2025-02-12T16:35:42Z","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":"2026-11-03T00:03:57.825751Z"}],"ghsa":[{"id":"GHSA-w9g2-3w7p-72g9","title":"Incorrect success value returned in vyper","description":"### Background\nDuring the audit of [Lido's Gate Seals](https://github.com/lidofinance/gate-seals) code [statemind](https://statemind.io) team identified a weird behavior of the code that uses `raw_call`: https://github.com/lidofinance/gate-seals/blob/051593e74df01a4131c485b4fda52e691cd4b7d8/contracts/GateSeal.vy#L164 .\n\nConstruction like this:\n```vyper\nsuccess = raw_call(\n    sealable,\n    _abi_encode(SEAL_DURATION_SECONDS, method_id=method_id(\"pauseFor(uint256)\")),\n    revert_on_failure=False\n)\n```\nwas not fully documented: https://docs.vyperlang.org/en/v0.3.7/built-in-functions.html#raw_call .\n\nThe documentation says that: if `max_outsize=0` it should return nothing and then it says that if `revert_on_failure=False` it should return a `success` flag in the tuple of response, but what if `max_outsize=0`  and `revert_on_failure=False`.\n\n\u003cimg width=\"715\" alt=\"image\" src=\"https://user-images.githubusercontent.com/22330612/232125364-d2b3bbac-0b4f-40cb-80ff-f55d8eafef44.png\"\u003e\n\n So the team started researching what exactly happened in that case, after some research we found that the Vyper compiler generates the wrong bytecode in that case, it generates the sequence:\n```\nCALL // call\nMLOAD // MLOAD is wrong since the CALL result is already stored in the stack\n```\n\n### Impact\nExample of buggy code:\n```vyper\n@external\ndef returnSome(calling: address, a: uint256) -\u003e bool:\n    success: bool = false\n    success = raw_call(\n        calling,\n        _abi_encode(a, method_id=method_id(\"a(uint256)\")),\n        revert_on_failure=False\n        )\n```\n\nany contract that uses the `raw_call` with `revert_on_failure=False` and `max_outsize=0` receives the wrong response from `raw_call`. Depending on the memory garbage, the result can be either `True` or `False`.\n\n### Patches\nFix by @charles-cooper https://github.com/vyperlang/vyper/commit/851f7a1b3aa2a36fd041e3d0ed38f9355a58c8ae\n\n### Workarounds\nThe simple workaround is always to put  `max_outsize\u003e0`.\nWorkaround example https://github.com/lidofinance/gate-seals/pull/5/files\n\n### References\nLido's fix: https://github.com/lidofinance/gate-seals/pull/5/files\n","status":"published","published":"2023-04-24T22:33:52Z","modified":"2024-11-19T16:31:36Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"},{"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"}],"cwes":["CWE-670"],"updated_at":"2026-11-02T14:38:21.777721Z"}],"nvd":[{"id":"CVE-2023-30629","description":"Vyper is a Pythonic Smart Contract Language for the ethereum virtual machine. In versions 0.3.1 through 0.3.7, the Vyper compiler generates the wrong bytecode. Any contract that uses the `raw_call` with `revert_on_failure=False` and `max_outsize=0` receives the wrong response from `raw_call`. Depending on the memory garbage, the result can be either `True` or `False`. A patch is available and, as of time of publication, anticipated to be part of Vyper 0.3.8. As a workaround, one may always put  `max_outsize\u003e0`.","status":"published","published":"2023-04-24T22:15:10.03Z","modified":"2026-06-17T05:55:11.67Z","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","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-670"],"updated_at":"2026-11-02T14:07:56.683259Z"}],"osv":[{"id":"CVE-2023-30629","title":"Vyper's raw_call with outsize=0 and revert_on_failure=False returns incorrect success value","description":"Vyper is a Pythonic Smart Contract Language for the ethereum virtual machine. In versions 0.3.1 through 0.3.7, the Vyper compiler generates the wrong bytecode. Any contract that uses the `raw_call` with `revert_on_failure=False` and `max_outsize=0` receives the wrong response from `raw_call`. Depending on the memory garbage, the result can be either `True` or `False`. A patch is available and, as of time of publication, anticipated to be part of Vyper 0.3.8. As a workaround, one may always put  `max_outsize\u003e0`.","status":"published","published":"2023-04-24T21:58:00.227Z","modified":"2026-10-28T02:30:34.697286971Z","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"}],"cwes":["CWE-670"],"updated_at":"2026-11-02T15:44:31.790231Z"},{"id":"GHSA-w9g2-3w7p-72g9","title":"Incorrect success value returned in vyper","description":"### Background\nDuring the audit of [Lido's Gate Seals](https://github.com/lidofinance/gate-seals) code [statemind](https://statemind.io) team identified a weird behavior of the code that uses `raw_call`: https://github.com/lidofinance/gate-seals/blob/051593e74df01a4131c485b4fda52e691cd4b7d8/contracts/GateSeal.vy#L164 .\n\nConstruction like this:\n```vyper\nsuccess = raw_call(\n    sealable,\n    _abi_encode(SEAL_DURATION_SECONDS, method_id=method_id(\"pauseFor(uint256)\")),\n    revert_on_failure=False\n)\n```\nwas not fully documented: https://docs.vyperlang.org/en/v0.3.7/built-in-functions.html#raw_call .\n\nThe documentation says that: if `max_outsize=0` it should return nothing and then it says that if `revert_on_failure=False` it should return a `success` flag in the tuple of response, but what if `max_outsize=0`  and `revert_on_failure=False`.\n\n\u003cimg width=\"715\" alt=\"image\" src=\"https://user-images.githubusercontent.com/22330612/232125364-d2b3bbac-0b4f-40cb-80ff-f55d8eafef44.png\"\u003e\n\n So the team started researching what exactly happened in that case, after some research we found that the Vyper compiler generates the wrong bytecode in that case, it generates the sequence:\n```\nCALL // call\nMLOAD // MLOAD is wrong since the CALL result is already stored in the stack\n```\n\n### Impact\nExample of buggy code:\n```vyper\n@external\ndef returnSome(calling: address, a: uint256) -\u003e bool:\n    success: bool = false\n    success = raw_call(\n        calling,\n        _abi_encode(a, method_id=method_id(\"a(uint256)\")),\n        revert_on_failure=False\n        )\n```\n\nany contract that uses the `raw_call` with `revert_on_failure=False` and `max_outsize=0` receives the wrong response from `raw_call`. Depending on the memory garbage, the result can be either `True` or `False`.\n\n### Patches\nFix by @charles-cooper https://github.com/vyperlang/vyper/commit/851f7a1b3aa2a36fd041e3d0ed38f9355a58c8ae\n\n### Workarounds\nThe simple workaround is always to put  `max_outsize\u003e0`.\nWorkaround example https://github.com/lidofinance/gate-seals/pull/5/files\n\n### References\nLido's fix: https://github.com/lidofinance/gate-seals/pull/5/files\n","status":"published","published":"2023-04-24T22:33:52Z","modified":"2026-09-10T03:50:01.176366652Z","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"},{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-670"],"updated_at":"2026-11-02T15:46:58.401149Z"},{"id":"PYSEC-2023-131","description":"Vyper is a Pythonic Smart Contract Language for the ethereum virtual machine. In versions 0.3.1 through 0.3.7, the Vyper compiler generates the wrong bytecode. Any contract that uses the `raw_call` with `revert_on_failure=False` and `max_outsize=0` receives the wrong response from `raw_call`. Depending on the memory garbage, the result can be either `True` or `False`. A patch is available and, as of time of publication, anticipated to be part of Vyper 0.3.8. As a workaround, one may always put  `max_outsize\u003e0`.","status":"published","published":"2023-04-24T22:15:00Z","modified":"2023-11-08T04:12:26.595556Z","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"}]}}