Out-of-bounds Write Affecting vyper package, versions [,0.3.8)


Severity

Recommended
0.0
high
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

Exploit Maturity
Proof of concept
EPSS
0.17% (55th percentile)

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  • Snyk IDSNYK-PYTHON-VYPER-5529832
  • published12 May 2023
  • disclosed12 May 2023
  • creditUnknown

Introduced: 12 May 2023

CVE-2023-31146  (opens in a new tab)
CWE-787  (opens in a new tab)

How to fix?

Upgrade vyper to version 0.3.8 or higher.

Overview

vyper is a Pythonic Smart Contract Language for the EVM.

Affected versions of this package are vulnerable to Out-of-bounds Write when assigning values to a dynarray whose source is the same dynarray. In that case, the length word of the dynarray is written before the data. The issue can cause data corruption across call frames.

PoC

@external
def should_revert() -> DynArray[uint256,3]:
    a: DynArray[uint256, 3] = [1, 2, 3]
    a = empty(DynArray[uint256, 3])
    a = [self.a[0], self.a[1], self.a[2]]
    return a  # if bug: returns [1,2,3]

References

CVSS Scores

version 3.1