CVE-2024-32481: vyper's range(start, start + N) reverts for negative numbers
First published: Thu Apr 25 2024(Updated: )
### Summary When looping over a `range` of the form `range(start, start + N)`, if `start` is negative, the execution will always revert. ### Details This issue is caused by an incorrect assertion inserted by the code generation of the range (`stmt.parse_For_range()`): https://github.com/vyperlang/vyper/blob/9136169468f317a53b4e7448389aa315f90b95ba/vyper/codegen/stmt.py#L286-L287 This assertion was introduced in https://github.com/vyperlang/vyper/commit/3de1415ee77a9244eb04bdb695e249d3ec9ed868 to fix https://github.com/advisories/GHSA-6r8q-pfpv-7cgj. The issue arises when `start` is signed, instead of using `sle`, `le` is used and `start` is interpreted as an unsigned integer for the comparison. If it is a negative number, its 255th bit is set to `1` and is hence interpreted as a very large unsigned integer making the assertion always fail. ### PoC ```Vyper @external def foo(): x:int256 = min_value(int256) # revert when it should not since we have the following assertion that fails: # [assert, [le, min_value(int256), max_value(int256) + 1 - 10]], for i in range(x, x + 10): pass ``` ### Patches patched in v0.4.0, specifically, https://github.com/vyperlang/vyper/pull/3679 disallows this form of `range()`. ### Impact Any contract having a `range(start, start + N)` where `start` is a signed integer with the possibility for `start` to be negative is affected. If a call goes through the loop while supplying a negative `start` the execution will revert.
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| pip/vyper | >=0.3.8<0.4.0 | 0.4.0 |
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Reference Links
- https://github.com/vyperlang/vyper/security/advisories/GHSA-ppx5-q359-pvwj
- https://github.com/vyperlang/vyper/commit/3de1415ee77a9244eb04bdb695e249d3ec9ed868
- https://github.com/vyperlang/vyper/commit/5319cfbe14951e007ccdb323257e5ada869b35d5
- https://github.com/vyperlang/vyper/blob/9136169468f317a53b4e7448389aa315f90b95ba/vyper/codegen/stmt.py#L286-L287
- https://nvd.nist.gov/vuln/detail/CVE-2024-32481
- https://github.com/advisories/GHSA-ppx5-q359-pvwj (Advisory)
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