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Medium, CVSS 6.3amended

Vyper: Return inside for loop more than 1 level deep

CVE-2020-37288GHSA-vg88-3v92-rjx2

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (vyper 0.2.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI vyper

    Affected
    >= 0.1.0b10, < 0.2.3
    Fixed in
    0.2.3

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
6.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2020-37288: 0.35% estimated exploitation activity in the next 30 days; percentile 28.34 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

VVE-2020-0002 Earlier today, we received a responsible disclosure of a potential issue from @michwill (developer of @curvefi) for Vyper users who use return statements inside for loops of nested internal calls. Returning inside a for loop causes an invalid jump dest, reverting the transaction unnecessarily. MWE: Impact Impact is minor, it is unlikely a user would encounter this problem unless they were working with nested calls, and return statements inside calls. Even in that scenario, you would encounter a revert which should be noticeable with adequate testing. In limited circumstances, this could cause a DoS attack for public contracts under certain conditions. Patches Fixed in https://github.com/vyperlang/vyper/pull/2110. Please upgrade to Vyper 0.2.3 Workarounds Not returning inside a for loop nested 2+ internal calls deep works as is: For more information If you have any questions or comments about this advisory: Chat with us in our gitter Open an issue in…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-vg88-3v92-rjx2

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GHSA-vg88-3v92-rjx2

  4. Revision 1 · created ·

    Published from ghsa record GHSA-vg88-3v92-rjx2

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2020-37288

Advisory: Vyper: Return inside for loop more than 1 level deep
IDs: CVE-2020-37288, GHSA-vg88-3v92-rjx2
Record: https://patchnext.com/advisories/ghsa-vg88-3v92-rjx2 (revision 4, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: vyper 0.2.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI vyper: affected >= 0.1.0b10, < 0.2.3; fixed in 0.2.3

## 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://github.com/advisories/GHSA-vg88-3v92-rjx2 (GitHub-reviewed advisory GHSA-vg88-3v92-rjx2 lists affected ranges: PyPI vyper >=0.1.0b10 <0.2.3)
- Verified: https://osv.dev/vulnerability/GHSA-vg88-3v92-rjx2 (OSV record GHSA-vg88-3v92-rjx2 lists affected ranges: PyPI vyper >=0.1.0b10 <0.2.3 (fixed))

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