CVE-2024-24564 – vyper

Package

Manager: pip
Name: vyper
Vulnerable Version: >=0 <0.4.0

Severity

Level: Low

CVSS v3.1: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS v4.0: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS: 0.00475 pctl0.63857

Details

Vyper's `extract32` can ready dirty memory ### Summary When using the built-in `extract32(b, start)`, if the `start` index provided has for side effect to update `b`, the byte array to extract `32` bytes from, it could be that some dirty memory is read and returned by `extract32`. As of v0.4.0 (specifically, commit https://github.com/vyperlang/vyper/commit/3d9c537142fb99b2672f21e2057f5f202cde194f), the compiler will panic instead of generating bytecode. ### Details Before evaluating `start`, the function `Extract32.build_IR` caches only: - The pointer in memory/storage to `b`: https://github.com/vyperlang/vyper/blob/10564dcc37756f3d3684b7a91fd8f4325a38c4d8/vyper/builtins/functions.py#L916-L918 - The length of `b`: https://github.com/vyperlang/vyper/blob/10564dcc37756f3d3684b7a91fd8f4325a38c4d8/vyper/builtins/functions.py#L920-L922 but do not cache the actual content of `b`. This means that if the evaluation of `start` changes `b`'s content and length, an outdated length will be used with the new content when extracting 32 bytes from `b`. ### PoC Calling the function `foo` of the following contract returns `b'uuuuuuuuuuuuuuuuuuuuuuuuuuu\x00\x00789'` meaning that `extract32` accessed some dirty memory. ```Vyper var:Bytes[96] @internal def bar() -> uint256: self.var = b'uuuuuuuuuuuuuuuuuuuuuuuuuuuuuu' self.var = b'' return 3 @external def foo() -> bytes32: self.var = b'abcdefghijklmnopqrstuvwxyz123456789' return extract32(self.var, self.bar(), output_type=bytes32) # returns b'uuuuuuuuuuuuuuuuuuuuuuuuuuu\x00\x00789' ``` ### Impact For contracts that are affected, it means that calling `extract32` returns dirty memory bytes instead of some expected output.

Metadata

Created: 2024-02-26T20:11:35Z
Modified: 2025-01-21T17:54:09Z
Source: https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2024/02/GHSA-4hwq-4cpm-8vmx/GHSA-4hwq-4cpm-8vmx.json
CWE IDs: ["CWE-125"]
Alternative ID: GHSA-4hwq-4cpm-8vmx
Finding: F111
Auto approve: 1