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High

incorrect storage layout for contracts containing large arrays

  • Disclosed: 13.12.2023
  • Updated: 11.10.2026 15:17

Impact

contracts containing large arrays might underallocate the number of slots they need. prior to v0.3.8, the calculation to determine how many slots a storage variable needed used math.ceil(type_.size_in_bytes / 32):

https://github.com/vyperlang/vyper/blob/6020b8bbf66b062d299d87bc7e4eddc4c9d1c157/vyper/semantics/validation/data_positions.py#L197

the intermediate floating point step can produce a rounding error if there are enough bits set in the IEEE-754 mantissa. roughly speaking, if type_.size_in_bytes is large (> 2**46), and slightly less than a power of 2, the calculation can overestimate how many slots are needed. if type_.size_in_bytes is slightly more than a power of 2, the calculation can underestimate how many slots are needed.

the following two example contracts can result in overwriting of the variable vulnerable:

vyper
large_array: address[2**64 + 1]  # type_.size_in_bytes == 32 * (2**64 + 1); math.ceil(type_.size_in_bytes / 32) < 2**64 + 1
vulnerable: uint256

# writing to self.large_array[2**64] will overwrite self.vulnerable
vyper
large_dynarray: DynArray[address, 2**64]  # Dynarray has a length word in front, its size in bytes is 32 * (2**64 + 1)
vulnerable: uint256

# writing to self.large_dynarray[2**64 - 1] will overwrite self.vulnerable

note that in the latter case, the risk of vulnerable being overwritten is relatively small, since it would cost roughly $1.45 million trillion USD at today's gas prices (gas price 20gwei, ETH ~= $1800) in order to extend the DynArray to its full container size.

Patches

patched by v0.3.8, specifically in commit https://github.com/vyperlang/vyper/commit/0bb7203b584e771b23536ba065a6efda457161bb.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Python (PyPI) vyper < 0.3.8 0.3.8

References

CVSS score 7.5/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness (CWE)
CWE-193
Platform
Python (PyPI)
Package
vyper
Disclosed
13.12.2023
Updated
11.10.2026 15:17

Sources and licenses

OSV / GitHub Advisory Database - PYSEC-2023-307 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-6m97-7527-mh74 - CC BY 4.0

Vulnerability history: vyper

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (47) in the archive
Total entries
47
First → latest
03.2020 10.2026
Without a fix
5
Exploited in attacks
0

Severity breakdown

  • Critical 3
  • High 14
  • Medium 20
  • Low 10

Disclosures per year

Severity:
  1. Vyper negative array index bounds checks
    Critical · 9.8 CVE-2024-24563 < 0.4.0 0.4.0
  2. Vyper's bounds check on built-in `slice()` function can be overflowed
    Critical · 9.8 CVE-2024-24561 < 0.4.0 0.4.0
  3. concat built-in can corrupt memory in vyper
    High · 7.3 CVE-2024-22419 >= 0.3.0, < 0.4.0 0.4.0
  4. incorrect storage layout for contracts containing large arrays this entry
    High · 7.5 CVE-2023-46247 < 0.3.8 0.3.8
  5. Vyper vulnerable to memory corruption in certain builtins utilizing `msize`
    High · 8.1 CVE-2023-42443 >= 0.3.4, < 0.3.10 0.3.10
  6. Vyper has incorrectly allocated named re-entrancy locks
    Critical · 8.7 CVE-2023-39363 >= 0.2.15, < 0.3.1 0.3.1
  7. Vyper vulnerable to incorrect ordering of arguments for kwargs passed to internal calls
    High · 7.5 CVE-2023-32059 < 0.3.8 0.3.8
  8. Vyper vulnerable to integer overflow in loop
    High · 7.5 CVE-2023-32058 < 0.3.8 0.3.8
  9. Vyper vulnerable to OOB DynArray access when array is on both LHS and RHS of an assignment
    High · 7.5 CVE-2023-31146 < 0.3.8 0.3.8
  10. vyper vulnerable to storage allocator overflow
    High · 7.5 CVE-2023-30837 < 0.3.8 0.3.8
  11. Incorrect success value returned in vyper
    High · 7.5 CVE-2023-30629 >= 0.3.1, < 0.3.8 0.3.8
  12. Multiple evaluation of contract address in call in vyper
    High · 7.5 CVE-2022-29255 < 0.3.4 0.3.4
  13. Vyper is a pythonic Smart Contract Language for the ethereum virtual machine. In affected versions, the return of `<iface>.returns_int128()` is not validated to fall within the bounds of `int128`. Thi
    High · 8.8 CVE-2022-24845 < 0.3.2 0.3.2
  14. Buffer Overflow in vyper
    High · 7.1 CVE-2022-24788 < 0.3.2 0.3.2
  15. Incorrect Comparison in Vyper
    High · 7.5 CVE-2022-24787 < 0.3.2 0.3.2
  16. Memory corruption when returning a literal struct with a private call inside of it
    High · 7.5 CVE-2021-41121 < 0.3.0 0.3.0
  17. Storage corruption due to variables overwritten by re-entrancy locks
    High ghsa-7f92-rr6w-cq64 >= 0.2.13, < 0.2.15 0.2.15

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