{"id":"CVE-2025-47774","state":"PUBLISHED","title":"Vyper's `slice()` may elide side-effects when output length is 0","description":"Vyper is the Pythonic Programming Language for the Ethereum Virtual Machine. In versions up to and including 0.4.2rc1, the `slice()` builtin can elide side effects when the output length is 0, and the source bytestring is a builtin (`msg.data` or `<address>.code`). The reason is that for these source locations, the check that `length >= 1` is skipped. The result is that a 0-length bytestring constructed with slice can be passed to `make_byte_array_copier`, which elides evaluation of its source argument when the max length is 0. The impact is that side effects in the `start` argument may be elided when the `length` argument is 0, e.g. `slice(msg.data, self.do_side_effect(), 0)`. The fix in pull request 4645 disallows any invocation of `slice()` with length 0, including for the ad hoc locations discussed in this advisory. The fix is expected to be part of version 0.4.2.","publishedAt":"2025-05-15T17:38:58.487Z","updatedAt":"2025-05-15T18:33:29.976Z","severity":{"score":2.9,"label":"Low","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P","source":"GitHub_M"},"assigner":"GitHub_M","products":["vyperlang vyper"],"affected":[{"vendor":"vyperlang","product":"vyper","versions":[{"version":"<= 0.4.2rc1","status":"affected"}]}],"references":["https://github.com/vyperlang/vyper/security/advisories/GHSA-3vcg-j39x-cwfm","https://github.com/vyperlang/vyper/pull/4645","https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/builtins/functions.py#L315-L319","https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/codegen/core.py#L189-L191"],"weaknesses":["CWE-691"],"ingestedAt":"2026-10-29T20:09:23.771Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/47xxx/CVE-2025-47774.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2025-47774","state":"PUBLISHED","datePublished":"2025-05-15T17:38:58.487Z","dateUpdated":"2025-05-15T18:33:29.976Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2025-05-09T19:49:35.619Z"},"containers":{"cna":{"title":"Vyper's `slice()` may elide side-effects when output length is 0","descriptions":[{"lang":"en","value":"Vyper is the Pythonic Programming Language for the Ethereum Virtual Machine. In versions up to and including 0.4.2rc1, the `slice()` builtin can elide side effects when the output length is 0, and the source bytestring is a builtin (`msg.data` or `<address>.code`). The reason is that for these source locations, the check that `length >= 1` is skipped. The result is that a 0-length bytestring constructed with slice can be passed to `make_byte_array_copier`, which elides evaluation of its source argument when the max length is 0. The impact is that side effects in the `start` argument may be elided when the `length` argument is 0, e.g. `slice(msg.data, self.do_side_effect(), 0)`. The fix in pull request 4645 disallows any invocation of `slice()` with length 0, including for the ad hoc locations discussed in this advisory. The fix is expected to be part of version 0.4.2."}],"affected":[{"vendor":"vyperlang","product":"vyper","versions":[{"version":"<= 0.4.2rc1","status":"affected"}]}],"references":[{"url":"https://github.com/vyperlang/vyper/security/advisories/GHSA-3vcg-j39x-cwfm","name":"https://github.com/vyperlang/vyper/security/advisories/GHSA-3vcg-j39x-cwfm","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/vyperlang/vyper/pull/4645","name":"https://github.com/vyperlang/vyper/pull/4645","tags":["x_refsource_MISC"]},{"url":"https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/builtins/functions.py#L315-L319","name":"https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/builtins/functions.py#L315-L319","tags":["x_refsource_MISC"]},{"url":"https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/codegen/core.py#L189-L191","name":"https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/codegen/core.py#L189-L191","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":2.9,"baseSeverity":"LOW","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-691","lang":"en","description":"CWE-691: Insufficient Control Flow Management","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2025-05-15T17:38:58.487Z"},"source":{"advisory":"GHSA-3vcg-j39x-cwfm","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2025-05-15T18:33:24.817738Z","id":"CVE-2025-47774","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-05-15T18:33:29.976Z"}}]}}}