Improper Control of Generation of Code ('Code Injection') Affecting vyper package, versions [0.3.4, 0.4.0)


Severity

Recommended
0.0
medium
0
10

CVSS assessment made by Snyk's Security Team

    Threat Intelligence

    Exploit Maturity
    Proof of concept
    EPSS
    0.04% (11th percentile)

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  • Snyk ID SNYK-PYTHON-VYPER-6674051
  • published 26 Apr 2024
  • disclosed 25 Apr 2024
  • credit cyberthirst

How to fix?

Upgrade vyper to version 0.4.0 or higher.

Overview

vyper is a Pythonic Smart Contract Language for the EVM.

Affected versions of this package are vulnerable to Improper Control of Generation of Code ('Code Injection') due to the build_IR function of the sqrt builtin not caching the argument to the stack, leading to potential double evaluation of the argument if it has side-effects. This could allow an attacker to manipulate the outcome of the sqrt function under certain conditions.

PoC


c: uint256

@internal
def some_decimal() -> decimal:
    self.c += 1
    return 1.0

@external
def foo() -> uint256:
    k: decimal = sqrt(self.some_decimal())
    return self.c

CVSS Scores

version 3.1
Expand this section

Snyk

Recommended
5.3 medium
  • Attack Vector (AV)
    Network
  • Attack Complexity (AC)
    Low
  • Privileges Required (PR)
    None
  • User Interaction (UI)
    None
  • Scope (S)
    Unchanged
  • Confidentiality (C)
    None
  • Integrity (I)
    Low
  • Availability (A)
    None