CVE-2024-32481 vyper's range(start, start + N) reverts for negative numbers
Attackers can cause smart contract execution to revert by supplying negative start values to range loops, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-32481?
CVE-2024-32481 is a medium-severity denial of service vulnerability in vyperlang vyper, published on 25 Apr 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Vyper is a pythonic Smart Contract Language for the Ethereum virtual machine. Starting in version 0.3.8 and prior to version 0.4.0b1, when looping over a `range` of the form `range(start, start + N)`, if `start` is negative, the execution will always revert. This issue is caused by an incorrect assertion inserted by the code generation of the range `stmt.parse_For_range()`. 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. 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. Version 0.4.0b1 fixes the issue.
Weakness: CWE-681
Which versions are affected by CVE-2024-32481?
3 open source packages ship an affected version, including vyper. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
vyper PyPI | From 0.3.8 | 0.4.0 |
vyper PyPI | From 0.3.8 | 0.4.0 |
vyper PyPI | From 0.3.8 | 0.4.0b1 |
Products include Vyperlang Vyper.
How do I fix CVE-2024-32481?
Upgrade vyper to a fixed version for your release line: 0.4.0 or 0.4.0b1.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-32481 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-32481 exists.
Other vulnerabilities in vyperlang vyper
- CVE-2024-24563 Vyper array negative index vulnerability
- CVE-2024-24561 Vyper bounds check on built-in `slice()` function can be overflowed
- CVE-2023-39363 Vyper incorrectly allocated named re-entrancy locks
- CVE-2022-24845 Integer bounds error in Vyper
- CVE-2022-29255 Multiple evaluation of contract address in call in vyper
Sources
Also known as GHSA-ppx5-q359-pvwj, PYSEC-2024-246.