CVE-2023-31146 Vyper vulnerable to OOB DynArray access when array is on both LHS and RHS of an assignment

What is CVE-2023-31146?

CVE-2023-31146 is a high-severity memory corruption vulnerability in vyperlang vyper, published on 11 May 2023. 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. Prior to version 0.3.8, during codegen, the length word of a dynarray is written before the data, which can result in out-of-bounds array access in the case where the dynarray is on both the lhs and rhs of an assignment. The issue can cause data corruption across call frames. The expected behavior is to revert due to out-of-bounds array access. Version 0.3.8 contains a patch for this issue.

Weakness: CWE-787

Which versions are affected by CVE-2023-31146?

3 open source packages ship an affected version, including vyper. It affects 1 product.

Products include Vyperlang Vyper.

How do I fix CVE-2023-31146?

Upgrade vyper to 0.3.8 or later.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2023-31146 being exploited?

There is no known exploitation of CVE-2023-31146 in the wild and no public exploit code.

Other vulnerabilities in vyperlang vyper

• CVE-2024-24563 Vyper array negative index vulnerability Critical 9.8
• CVE-2024-24561 Vyper bounds check on built-in `slice()` function can be overflowed Critical 9.8
• CVE-2023-39363 Vyper incorrectly allocated named re-entrancy locks Critical 9.1
• CVE-2022-24845 Integer bounds error in Vyper High 8.8
• CVE-2022-29255 Multiple evaluation of contract address in call in vyper High 8.2

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-3p37-3636-q8wv, PYSEC-2023-77.