Out-of-bounds Read Affecting vyper package, versions [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-6277565
  • published 27 Feb 2024
  • disclosed 26 Feb 2024
  • credit trocher

How to fix?

There is no fixed version for vyper.

Overview

vyper is a Pythonic Smart Contract Language for the EVM.

Affected versions of this package are vulnerable to Out-of-bounds Read due to the extract32 function's caching mechanism. An attacker can access and return dirty memory bytes instead of the expected output by manipulating the start index to change b's content and length.

PoC


var:Bytes[96]

@internal
def bar() -> uint256:
    self.var = b'uuuuuuuuuuuuuuuuuuuuuuuuuuuuuu'
    self.var = b''
    return 3

@external
def foo() -> bytes32:
    self.var = b'abcdefghijklmnopqrstuvwxyz123456789'
    return extract32(self.var, self.bar(), output_type=bytes32)
    # returns b'uuuuuuuuuuuuuuuuuuuuuuuuuuu\x00\x00789'

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)
    Low
  • Integrity (I)
    None
  • Availability (A)
    None