CWE
787
Advisory Published
Advisory Published
Updated

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

First published: Thu May 11 2023(Updated: )

### Impact during codegen, the length word of a dynarray is written before the data, which can result in OOB array access in the case where the dynarray is on both the lhs and rhs of an assignment. here is a minimal example producing the issue: ```vyper a:DynArray[uint256,3] @external def test() -> DynArray[uint256,3]: self.a = [1,2,3] self.a = empty(DynArray[uint256,3]) self.a = [self.a[0],self.a[1],self.a[2]] return self.a # return [1,2,3] ``` and here is an example demonstrating the issue can cause data corruption across call frames: ```vyper @external def test() -> DynArray[uint256,3]: self.a() return self.b() # return [1,2,3] @internal def a(): a: uint256 = 0 b: uint256 = 1 c: uint256 = 2 d: uint256 = 3 @internal def b() -> DynArray[uint256,3]: a: DynArray[uint256,3] = empty(DynArray[uint256,3]) a = [a[0],a[1],a[2]] return a ``` examples involving append and pop: ```vyper @internal def foo(): c: DynArray[uint256, 1] = [] c.append(c[0]) ``` ```vyper @internal def foo(): c: DynArray[uint256, 1] = [1] c[0] = c.pop() ``` the expected behavior in all of the above cases is to revert due to oob array access. ### Patches patched in 4f8289a81206f767df1900ac48f485d90fc87edb ### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_ ### References _Are there any links users can visit to find out more?_

Credit: security-advisories@github.com security-advisories@github.com security-advisories@github.com

Affected SoftwareAffected VersionHow to fix
pip/vyper<0.3.8
0.3.8
Vyperlang Vyper<0.3.8

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Frequently Asked Questions

  • What is CVE-2023-31146?

    CVE-2023-31146 is a vulnerability in the Vyper smart contract language for the Ethereum virtual machine.

  • What is the severity of CVE-2023-31146?

    CVE-2023-31146 has a severity rating of critical (9.1).

  • What is the affected software for CVE-2023-31146?

    The affected software for CVE-2023-31146 is Vyper version up to exclusive 0.3.8.

  • How can this vulnerability be exploited?

    This vulnerability can be exploited by performing out-of-bounds array access in the case where a dynarray is on both the lhs and rhs of an assignment.

  • How can I fix CVE-2023-31146?

    To fix CVE-2023-31146, upgrade to Vyper version 0.3.8 or later.

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