Vyper negative array index bounds checks

Exploitation

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

CVSS

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

EPSS

• CVE-2024-24563: 1.54% estimated exploitation activity in the next 30 days; percentile 74.92 (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.

Summary Arrays can be keyed by a signed integer, while they are defined for unsigned integers only. The typechecker doesn't throw when spotting the usage of an int as an index for an array. Typically, negative integers are filtered out at runtime by the bounds checker, but small enough (i.e. large in magnitude, ex. -2255 + 5) quantities combined with large enough arrays (at least 2255 in length) can pass the bounds checker, resulting in unexpected behavior. A contract search was performed, and no production contracts were found to be impacted. Details The typechecker allows the usage of signed integers to be used as indexes to arrays. The vulnerability is present in different forms in all versions. Here is an example from 0.3.10: https://github.com/vyperlang/vyper/blob/c150fc49ee9375a930d177044559b83cb95f7963/vyper/semantics/types/subscriptable.py#L127-L137 As can be seen, the validation is performed against IntegerT.any(). PoC If the array is sufficiently large, it can be indexed…

Published by the source

7 Feb 2024, 17:27 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:27 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-52xq-j7v9-v4v2

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-52xq-j7v9-v4v2

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# Patch Next advisory brief: CVE-2024-24563

Advisory: Vyper negative array index bounds checks
IDs: CVE-2024-24563, GHSA-52xq-j7v9-v4v2
Record: https://patchnext.com/advisories/cve-2024-24563 (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: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: vyper 0.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI vyper: affected < 0.4.0; fixed in 0.4.0

## 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-52xq-j7v9-v4v2 (OSV record GHSA-52xq-j7v9-v4v2 lists affected ranges: PyPI vyper >=0 <0.4.0 (fixed))
- Verified: https://github.com/advisories/GHSA-52xq-j7v9-v4v2 (GitHub-reviewed advisory GHSA-52xq-j7v9-v4v2 lists affected ranges: PyPI vyper >=0 <0.4.0)

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