GHSA-vg88-3v92-rjx2: Vyper Return Inside For Loop More Vulnerability

MODERATE
Share
CWE-691
Published
Advisory Summary

GHSA-vg88-3v92-rjx2 is a MODERATE return inside for loop more vulnerability (CWE-691: Insufficient Control Flow Management) affecting Vyper libraries in the PyPI ecosystem. The issue involves return inside for loop more than 1 level deep. Remediation is available by upgrading affected packages to version 0.2.3.

GHSA-vg88-3v92-rjx2 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-vg88-3v92-rjx2
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-691: Insufficient Control Flow Management
Affected Product Vyper
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix GHSA-vg88-3v92-rjx2

To remediate this vulnerability, upgrade all affected Vyper dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

vyper fixed: 0.2.3 
pip install vyper>=0.2.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show vyper

How to Check if You Are Affected

To determine whether your Python environment is affected by GHSA-vg88-3v92-rjx2, inspect your installed packages using pip:

pip show vyper

Analyze the terminal output to locate any version of Vyper in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.2.3), your application is affected.

Note: The pip show vyper command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-691: Insufficient Control Flow Management, where the code does not sufficiently manage its control flow during execution, creating conditions in which the control flow can be modified in unexpected ways. In Vyper, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

# 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: ```python @internal def _baz(): for i in range(1): return # Stack underflow happens here @internal def _bar(): self._baz() @external def foo(): self._bar() ``` ### 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](https://pypi.org/project/vyper/) ### Workarounds Not returning inside a for loop nested 2+ internal calls deep works as is: ```python @internal def _baz(): for i in range(1): pass return # This works fine @internal def _bar(): self._baz() @external def foo(): self._bar() ``` ### For more information If you have any questions or comments about this advisory: * Chat with us in [our gitter ](https://gitter.im/vyperlang/community) * Open an issue in [https://github.com/vyperlang/vyper](https://github.com/vyperlang/vyper) * Email us at [security@vyperlang.org](mailto:security@vyperlang.org)

GHSA-vg88-3v92-rjx2 Affected Vyper Versions

1 component(s)
Fixed Versions:
0.2.3
Product / Package Ecosystem Affected Versions Fixed Version
vyper
pypi/vyper
PyPI
≥ 0.1.0b10
< 0.2.3
0.2.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/vyperlang/vyper/security/advisories/GHSA-vg88-3v92-rjx2
Vyper Source Repository REPOSITORY
https://github.com/vyperlang/vyper/pull/2110
Security Fix Commit FIX COMMIT
https://github.com/vyperlang/vyper/commit/a1d92e5eb968a34a23850359656aee23334adb90
Vyper Source Repository REPOSITORY
https://github.com/vyperlang/vyper
Vyper Release RELEASE
https://github.com/vyperlang/vyper/releases/tag/v0.2.3

Frequently Asked Questions

What is GHSA-vg88-3v92-rjx2?
GHSA-vg88-3v92-rjx2 is a security vulnerability in Vyper involving Return inside for loop more than 1 level deep under CWE-691: Insufficient Control Flow Management.
Which Vyper versions are affected?
Affected versions include releases prior to 0.2.3 across affected packages: vyper.
What version fixes GHSA-vg88-3v92-rjx2?
Upgrading to 0.2.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is vyper affected?
Yes, vyper is affected in releases prior to 0.2.3. Upgrade your dependency to 0.2.3 or later.
What CWE is associated with GHSA-vg88-3v92-rjx2?
GHSA-vg88-3v92-rjx2 is classified under CWE-691: Insufficient Control Flow Management (The code does not sufficiently manage its control flow during execution, creating conditions in which the control flow can be modified in unexpected ways.).
How can I check PyPI dependencies for GHSA-vg88-3v92-rjx2?
Run the dependency tree command: 'pip show vyper'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vg88-3v92-rjx2",
  "modified" : "2026-10-06T15:20:11Z",
  "published" : "2026-10-06T15:20:10Z",
  "aliases" : [ ],
  "summary" : "Vyper: Return inside for loop more than 1 level deep",
  "details" : "# VVE-2020-0002\nEarlier 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.\n\nMWE:\n```python\n@internal\ndef _baz():\n    for i in range(1):\n        return  # Stack underflow happens here\n\n@internal\ndef _bar():\n    self._baz()\n\n@external\ndef foo():\n    self._bar()\n```\n\n### Impact\nImpact 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.\n\n### Patches\nFixed in https://github.com/vyperlang/vyper/pull/2110. Please upgrade to [Vyper 0.2.3](https://pypi.org/project/vyper/)\n\n### Workarounds\nNot returning inside a for loop nested 2+ internal calls deep works as is:\n```python\n@internal\ndef _baz():\n    for i in range(1):\n        pass\n    return  # This works fine\n\n@internal\ndef _bar():\n    self._baz()\n\n@external\ndef foo():\n    self._bar()\n```\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Chat with us in [our gitter ](https://gitter.im/vyperlang/community)\n* Open an issue in [https://github.com/vyperlang/vyper](https://github.com/vyperlang/vyper)\n* Email us at [security@vyperlang.org](mailto:security@vyperlang.org)",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "vyper"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.1.0b10"
      }, {
        "fixed" : "0.2.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/vyperlang/vyper/security/advisories/GHSA-vg88-3v92-rjx2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vyperlang/vyper/pull/2110"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vyperlang/vyper/commit/a1d92e5eb968a34a23850359656aee23334adb90"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/vyperlang/vyper"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vyperlang/vyper/releases/tag/v0.2.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-691" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-06T15:20:10Z",
    "nvd_published_at" : null
  }
}