Vyper is the Pythonic Programming Language for the Ethereum Virtual Machine. In versions up to and including 0.4.2rc1, `concat()` may skip evaluation of side effects when the length of an argument is zero. This is due to a fastpath in the implementation which skips evaluation of argument expressions when their length is zero. In practice, it would be very unusual in user code to construct zero-length bytestrings using an expression with side-effects, since zero-length bytestrings are typically constructed with the empty literal `b""`; the only way to construct an empty bytestring which has side effects would be with the ternary operator introduced in v0.3.8, e.g. `b"" if self.do_some_side_effect() else b""`. The fix is available in pull request 4644 and expected to be part of the 0.4.2 release. As a workaround, don't have side effects in expressions which construct zero-length bytestrings.
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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, `concat()` may skip evaluation of side effects when the length of an argument is zero. This is due to a fastpath in the implementation which skips evaluation of argument expressions when their length is zero. In practice, it would be very unusual in user code to construct zero-length bytestrings using an expression with side-effects, since zero-length bytestrings are typically constructed with the empty literal `b""`; the only way to construct an empty bytestring which has side effects would be with the ternary operator introduced in v0.3.8, e.g. `b"" if self.do_some_side_effect() else b""`. The fix is available in pull request 4644 and expected to be part of the 0.4.2 release. As a workaround, don't have side effects in expressions which construct zero-length bytestrings. | |
Title | Vyper's `concat()` builtin may elide side-effects for zero-length arguments | |
Weaknesses | CWE-691 | |
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Status: PUBLISHED
Assigner: GitHub_M
Published: 2025-05-15T17:24:03.442Z
Updated: 2025-05-15T18:37:33.747Z
Reserved: 2025-05-05T16:53:10.374Z
Link: CVE-2025-47285

Updated: 2025-05-15T18:37:29.072Z

Status : Awaiting Analysis
Published: 2025-05-15T18:15:38.177
Modified: 2025-05-16T14:43:26.160
Link: CVE-2025-47285

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