Vyper's bounds check on built-in slice() function can be overflowed

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-2024-24561: 0.90% estimated exploitation activity in the next 30 days; percentile 59.76 (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 The bounds check for slices does not account for the ability for start + length to overflow when the values aren't literals. If a slice() function uses a non-literal argument for the start or length variable, this creates the ability for an attacker to overflow the bounds check. This issue can be used to do OOB access to storage, memory or calldata addresses. It can also be used to corrupt the length slot of the respective array. A contract search was performed and no vulnerable contracts were found in production. tracking in issue https://github.com/vyperlang/vyper/issues/3756. patched in https://github.com/vyperlang/vyper/pull/3818. Details Here the flow for storage is supposed, but it is generalizable also for the other locations. When calling slice() on a storage value, there are compile time bounds checks if the start and length values are literals, but of course this cannot happen if they are passed values: At runtime, we perform the following equivalent check, but the…

Published by the source

1 Feb 2024, 20:51 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-9x7f-gwxq-6f2c

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9x7f-gwxq-6f2c

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# Patch Next advisory brief: CVE-2024-24561

Advisory: Vyper's bounds check on built-in `slice()` function can be overflowed
IDs: CVE-2024-24561, GHSA-9x7f-gwxq-6f2c
Record: https://patchnext.com/advisories/cve-2024-24561 (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 <= 0.3.10; 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-9x7f-gwxq-6f2c (OSV record GHSA-9x7f-gwxq-6f2c lists affected ranges: PyPI vyper >=0 <0.4.0 (fixed))
- Verified: https://github.com/advisories/GHSA-9x7f-gwxq-6f2c (GitHub-reviewed advisory GHSA-9x7f-gwxq-6f2c lists affected ranges: PyPI vyper >=0 <=0.3.10)

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