GHSA-4hwq-4cpm-8vmx
First published: Mon Feb 26 2024(Updated: )
### 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`. ### 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 This means that if the evaluation of `start` changes `b`'s content and length, an outdated length will be used with the new content when extracting 32 bytes from `b`.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.
| Affected Software | Affected Version | How to fix |
|---|---|---|
| pip/vyper | <=0.3.10 |
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Reference Links
- https://github.com/vyperlang/vyper/security/advisories/GHSA-4hwq-4cpm-8vmx
- https://github.com/vyperlang/vyper/blob/10564dcc37756f3d3684b7a91fd8f4325a38c4d8/vyper/builtins/functions.py#L916-L918
- https://github.com/vyperlang/vyper/blob/10564dcc37756f3d3684b7a91fd8f4325a38c4d8/vyper/builtins/functions.py#L920-L922
- https://nvd.nist.gov/vuln/detail/CVE-2024-24564
- https://github.com/advisories/GHSA-4hwq-4cpm-8vmx (Advisory)
- agent/weakness
- agent/softwarecombine
- agent/first-publish-date
- agent/event
- agent/description
- agent/type
- collector/github-advisory-latest
- source/GitHub
- alias/GHSA-4hwq-4cpm-8vmx
- alias/CVE-2024-24564
- agent/software-canonical-lookup
- agent/severity
- agent/last-modified-date
- agent/references
- agent/tags
- collector/github-advisory
- package-manager/pip