CVE-2023-31146

Out-of-bounds array access in Vyper (before version 0.3.8)

• CVSS 9.1
• CWE-787
• Memory Corruption
• Remote

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.

CVE

CVE-2023-31146

CWE

CWE-787

CVSS base score

9.1

Published

2023-05-11

OWASP

A03 Injection

Orthogonal defect classification

Algorithm

Code defect classification

Incorrect Algorithm

Category

Memory Corruption

Subcategory

Out-of-Bound Accesses

Accessibility scope

Remote

Impact

Arbitrary Code Execution

Fixed by upgrading

Yes

Solution

Update to Vyper version 0.3.8 or higher

class DynamicArray:
    def __init__(self):
        self.data = []
    
    def append(self, value):
        self.data.append(value)
    
    def get(self, index):
        return self.data[index]
    
    def set(self, index, value):
        self.data[index] = value

array = DynamicArray()
array.append(1)
array.append(2)

array.set(2, 3)
print(array.get(2))

class DynamicArray:
    def __init__(self):
        self.data = []
    
    def append(self, value):
        self.data.append(value)
    
    def get(self, index):
        if index < 0 or index >= len(self.data):
            raise IndexError("Array index out of bounds")
        return self.data[index]
    
    def set(self, index, value):
        if index < 0 or index >= len(self.data):
            raise IndexError("Array index out of bounds")
        self.data[index] = value

array = DynamicArray()
array.append(1)
array.append(2)

try:
    array.set(2, 3) 
    print(array.get(2))
except IndexError as e:
    print(e)

@misc{vaitp:cve202331146,
  title        = {{Out-of-bounds array access in Vyper (before version 0.3.8) }},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2023},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2023-31146},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2023-31146/}}
}