CVE-2025-47285
Vyper's `concat()` builtin may elide side-effects for zero-length arguments
We use these services and cookies to improve your user experience. You may opt out if you wish, however, this may limit some features on this site.
Please see our statement on Data Privacy.
Vyper's `concat()` builtin may elide side-effects for zero-length arguments
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.
Reserved 2025-05-05 | Published 2025-05-15 | Updated 2025-05-15 | Assigner GitHub_MCWE-691: Insufficient Control Flow Management
github.com/.../vyper/security/advisories/GHSA-qhr6-mgqr-mchm
github.com/vyperlang/vyper/pull/4644
github.com/...74676170b8a6eaa316/vyper/builtins/functions.py
Support options
