CVE-2023-32675: Vyper Vyper's Nonpayable Default Functions Are Vulnerability

MODERATE
Advisory Identifier: GHSA-vxmm-cwh2-q762
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CVSS 3.7
CWE-670
Published
Advisory Summary

CVE-2023-32675 is a MODERATE (CVSS 3.7) vyper's nonpayable default functions are vulnerability (CWE-670: Always-Incorrect Control Flow Implementation) affecting Vyper libraries in the PyPI ecosystem. The issue involves vyper's nonpayable default functions are sometimes payable. Remediation is available by upgrading affected packages to version 0.3.8.

CVE-2023-32675 at a Glance

CVE Identifier CVE-2023-32675
GHSA Identifier GHSA-vxmm-cwh2-q762
Severity MODERATE
CVSS v3.1 Base Score 3.7
CWE Classification CWE-670: Always-Incorrect Control Flow Implementation
Affected Product Vyper
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 3.7

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2023-32675

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: 0.3.8 
pip install vyper>=0.3.8
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 CVE-2023-32675, 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 0.3.8), 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-670: Always-Incorrect Control Flow Implementation, where the code contains a control flow path that does not reflect the algorithm that the path is intended to implement, leading to incorrect behavior any time this path is navigated. 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

### Impact in contracts with at least one regular nonpayable function, due to the callvalue check being inside of the selector section, it is possible to send funds to the default function by using less than 4 bytes of calldata, even if the default function is marked `nonpayable`. this applies to contracts compiled with vyper<=0.3.7. ```vyper # @version 0.3.7 # implicitly nonpayable @external def foo() -> uint256: return 1 # implicitly nonpayable @external def __default__(): # could receive ether here pass ``` ### Patches this was fixed by the removal of the global calldatasize check in https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520. ### Workarounds don't use nonpayable default functions

CVE-2023-32675 Affected Vyper Versions

1 component(s)
Fixed Versions:
0.3.8
Product / Package Ecosystem Affected Versions Fixed Version
vyper
pypi/vyper
PyPI
< 0.3.8
0.3.8

References

GitHub Advisory / Wiki ADVISORY
https://github.com/vyperlang/vyper/security/advisories/GHSA-vxmm-cwh2-q762
NVD — CVE-2023-32675 NVD
https://nvd.nist.gov/vuln/detail/CVE-2023-32675
Security Fix Commit FIX COMMIT
https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520
Security Fix Commit FIX COMMIT
https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520.
Security Fix Commit FIX COMMIT
https://github.com/vyperlang/vyper/commit/903727006c1e5ebef99fa9fd5d51d62bd33d72a9
Vyper Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-80.yaml
Vyper Source Repository REPOSITORY
https://github.com/vyperlang/vyper

Frequently Asked Questions

What is CVE-2023-32675?
CVE-2023-32675 is a security vulnerability in Vyper involving Vyper's nonpayable default functions are sometimes payable under CWE-670: Always-Incorrect Control Flow Implementation.
Which Vyper versions are affected?
Affected versions include releases prior to 0.3.8 across affected packages: vyper.
What version fixes CVE-2023-32675?
Upgrading to 0.3.8 (or the latest patched release for your respective branch) resolves the vulnerability.
Is vyper affected?
Yes, vyper is affected in releases prior to 0.3.8. Upgrade your dependency to 0.3.8 or later.
What is the CVSS score of CVE-2023-32675?
CVE-2023-32675 has a CVSS v3.1 base score of 3.7 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2023-32675?
CVE-2023-32675 is classified under CWE-670: Always-Incorrect Control Flow Implementation (The code contains a control flow path that does not reflect the algorithm that the path is intended to implement, leading to incorrect behavior any time this path is navigated.).
How can I check PyPI dependencies for CVE-2023-32675?
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-vxmm-cwh2-q762",
  "modified" : "2024-11-19T16:42:42Z",
  "published" : "2023-05-22T20:35:46Z",
  "aliases" : [ "CVE-2023-32675" ],
  "summary" : "Vyper's nonpayable default functions are sometimes payable",
  "details" : "### Impact\nin contracts with at least one regular nonpayable function, due to the callvalue check being inside of the selector section, it is possible to send funds to the default function by using less than 4 bytes of calldata, even if the default function is marked `nonpayable`. this applies to contracts compiled with vyper<=0.3.7.\n```vyper\n# @version 0.3.7\n\n# implicitly nonpayable\n@external\ndef foo() -> uint256:\n    return 1\n\n# implicitly nonpayable\n@external\ndef __default__():\n    # could receive ether here\n    pass\n```\n\n### Patches\nthis was fixed by the removal of the global calldatasize check in https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520.\n\n### Workarounds\ndon't use nonpayable default functions\n\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "vyper"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.3.8"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/vyperlang/vyper/security/advisories/GHSA-vxmm-cwh2-q762"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-32675"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520."
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vyperlang/vyper/commit/903727006c1e5ebef99fa9fd5d51d62bd33d72a9"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-80.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/vyperlang/vyper"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-670" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-05-22T20:35:46Z",
    "nvd_published_at" : "2023-05-19T20:15:09Z"
  }
}