incorrect storage layout for contracts containing large arrays

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS

• CVE-2023-46247: 0.69% estimated exploitation activity in the next 30 days; percentile 52.92 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.sizeinbytes / 32): https://github.com/vyperlang/vyper/blob/6020b8bbf66b062d299d87bc7e4eddc4c9d1c157/vyper/semantics/validation/datapositions.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.sizeinbytes is large ( 246), and slightly less than a power of 2, the calculation can overestimate how many slots are needed. if type.sizeinbytes 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: 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…

Published by the source

13 Dec 2023, 13:18 UTC

Last modified by the source

10 Sep 2026, 03:49 UTC

Source last checked

26 Oct 2026, 13:27 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-6m97-7527-mh74

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-6m97-7527-mh74

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# Patch Next advisory brief: CVE-2023-46247

Advisory: incorrect storage layout for contracts containing large arrays
IDs: CVE-2023-46247, GHSA-6m97-7527-mh74
Record: https://patchnext.com/advisories/cve-2023-46247 (revision 2, source checked 26 Oct 2026, 13:27 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: vyper 0.3.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI vyper: affected <= 0.3.7; fixed in 0.3.8

## Suggested inspection (read-only)
- `python -m pip show vyper`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on vyper.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-6m97-7527-mh74 (OSV record GHSA-6m97-7527-mh74 lists affected ranges: PyPI vyper >=0 <0.3.8 (fixed))
- Verified: https://github.com/advisories/GHSA-6m97-7527-mh74 (GitHub-reviewed advisory GHSA-6m97-7527-mh74 lists affected ranges: PyPI vyper >=0 <=0.3.7)

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