Vyper: Return inside for loop more than 1 level deep

{
  "id": "2f3ab9de0e56727886ac327778321e62c563a4c11cdbf971d3019b34b796cf4b",
  "url": "https://osv.dev/vulnerability/GHSA-vg88-3v92-rjx2",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Vyper: Return inside for loop more than 1 level deep",
    "summary": "# 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]",
    "evidence": "osv:GHSA-vg88-3v92-rjx2",
    "products": [
      {
        "name": {
          "value": "vyper",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.2.3",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "0.1.0b10",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.1.0b11",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.1.0b12",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.1.0b13",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.1.0b14",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.1.0b15",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.1.0b16",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.1.0b17",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.2.1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.2.2",
            "evidence": "/affected/0/versions"
          }
        ]
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "GHSA-vg88-3v92-rjx2",
      "aliases": [
        "CVE-2020-37288",
        "GHSA-vg88-3v92-rjx2"
      ],
      "metrics": [
        {
          "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": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0.1.0b10"
                },
                {
                  "fixed": "0.2.3"
                }
              ]
            }
          ],
          "package": {
            "name": "vyper",
            "purl": "pkg:pypi/vyper",
            "ecosystem": "PyPI"
          },
          "versions": [
            "0.1.0b10",
            "0.1.0b11",
            "0.1.0b12",
            "0.1.0b13",
            "0.1.0b14",
            "0.1.0b15",
            "0.1.0b16",
            "0.1.0b17",
            "0.2.1",
            "0.2.2"
          ],
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-vg88-3v92-rjx2/GHSA-vg88-3v92-rjx2.json"
          }
        }
      ],
      "modified": "2026-10-24T02:56:09.007506586Z",
      "provider": "osv",
      "references": [
        "https://github.com/vyperlang/vyper/security/advisories/GHSA-vg88-3v92-rjx2",
        "https://github.com/vyperlang/vyper/pull/2110",
        "https://github.com/vyperlang/vyper/commit/a1d92e5eb968a34a23850359656aee23334adb90",
        "https://github.com/vyperlang/vyper",
        "https://github.com/vyperlang/vyper/releases/tag/v0.2.3"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-691"
        ],
        "severity": "MODERATE",
        "github_reviewed": true,
        "nvd_published_at": null,
        "github_reviewed_at": "2026-10-06T15:20:10Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2020-37288",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 428179,
  "published_at": "2026-10-06T15:20:10+00:00"
}