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.
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Thu, 15 May 2025 19:15:00 +0000
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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. | |
Title | Vyper's `slice()` may elide side-effects when output length is 0 | |
Weaknesses | CWE-691 | |
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Status: PUBLISHED
Assigner: GitHub_M
Published: 2025-05-15T17:38:58.487Z
Updated: 2025-05-15T18:33:29.976Z
Reserved: 2025-05-09T19:49:35.619Z
Link: CVE-2025-47774

Updated: 2025-05-15T18:33:27.138Z

Status : Awaiting Analysis
Published: 2025-05-15T18:15:38.440
Modified: 2025-05-16T14:43:26.160
Link: CVE-2025-47774

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