{"id":"GHSA-w9g2-3w7p-72g9","summary":"Incorrect success value returned in vyper","details":"### 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","aliases":["CVE-2023-30629","PYSEC-2023-131"],"modified":"2024-11-19T16:47:04.247397Z","published":"2023-04-24T22:33:52Z","database_specific":{"github_reviewed_at":"2023-04-24T22:33:52Z","nvd_published_at":"2023-04-24T22:15:10Z","cwe_ids":["CWE-670"],"severity":"HIGH","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/vyperlang/vyper/security/advisories/GHSA-w9g2-3w7p-72g9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-30629"},{"type":"WEB","url":"https://github.com/lidofinance/gate-seals/pull/5/files"},{"type":"WEB","url":"https://github.com/vyperlang/vyper/commit/851f7a1b3aa2a36fd041e3d0ed38f9355a58c8ae"},{"type":"WEB","url":"https://docs.vyperlang.org/en/v0.3.7/built-in-functions.html#raw_call"},{"type":"WEB","url":"https://github.com/lidofinance/gate-seals/blob/051593e74df01a4131c485b4fda52e691cd4b7d8/contracts/GateSeal.vy#L164"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-131.yaml"},{"type":"PACKAGE","url":"https://github.com/vyperlang/vyper"}],"affected":[{"package":{"name":"vyper","ecosystem":"PyPI","purl":"pkg:pypi/vyper"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.1"},{"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"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2023/04/GHSA-w9g2-3w7p-72g9/GHSA-w9g2-3w7p-72g9.json"}}],"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"},{"type":"CVSS_V4","score":"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"}]}