CVE-2025-47774 – vyper

Package

Manager: pip
Name: vyper
Vulnerable Version: >=0 <=0.4.2rc1

Severity

Level: Low

CVSS v3.1: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H/E:F/RL:O/RC:C

CVSS v4.0: 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

EPSS: 0.00063 pctl0.19949

Details

Vyper's `slice()` may elide side-effects when output length is 0 ### Impact 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: https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/builtins/functions.py#L315-L319 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: https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/codegen/core.py#L189-L191 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 following example illustrates how the issue would look in user code ```vyper counter: public(uint256) @external def test() -> Bytes[10]: b: Bytes[10] = slice(msg.data, self.side_effect(), 0) return b def side_effect() -> uint256: self.counter += 1 return 0 ``` the severity assigned is low, since this is not a very useful pattern and unlikely to be found in user code. ### Patches the fix is tracked in https://github.com/vyperlang/vyper/pull/4645, which disallows any invocation of `slice()` with length 0, including for the ad hoc locations discussed in this advisory. ### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_ ### References _Are there any links users can visit to find out more?_

Metadata

Created: 2025-05-16T14:13:29Z
Modified: 2025-05-16T14:13:29Z
Source: https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2025/05/GHSA-3vcg-j39x-cwfm/GHSA-3vcg-j39x-cwfm.json
CWE IDs: ["CWE-691"]
Alternative ID: GHSA-3vcg-j39x-cwfm
Finding: F111
Auto approve: 1