CVE-2025-47774
Vyper's `slice()` may elide side-effects when output length is 0
Severity Score
Exploit Likelihood
Affected Versions
Public Exploits
0Exploited in Wild
-Decision
Descriptions
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.
CVSS Scores
SSVC
- Decision:Track
Timeline
- 2025-05-09 CVE Reserved
- 2025-05-15 CVE Published
- 2025-05-15 CVE Updated
- 2025-06-16 EPSS Updated
- ---------- Exploited in Wild
- ---------- KEV Due Date
- ---------- First Exploit
CWE
- CWE-691: Insufficient Control Flow Management
CAPEC
References (4)
URL | Tag | Source |
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https://github.com/vyperlang/vyper/security/advisories/GHSA-3vcg-j39x-cwfm | X_refsource_confirm | |
https://github.com/vyperlang/vyper/pull/4645 | X_refsource_misc | |
https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/builtins/functions.py#L315-L319 | X_refsource_misc | |
https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/codegen/core.py#L189-L191 | X_refsource_misc |
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