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Vulnerabilities

Vulnerability · CVE-2020-37288

Vyper: Return inside for loop more than 1 level deep

Published Oct 6, 2026 · catalog updated Oct 24, 2026 · Vyper: Return inside for

Last checked Oct 25, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2020-37288. EPSS is 0.35%. Act only if a listed version of Vyper: Return inside for is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Vyper: Return inside for).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.35%
Remediation
Advisory link
Affected products
PyPI vyper

# 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](https://pypi.org/project/vyper/) ### 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 ](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)

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • PyPI vyper0.1.0b10 → 0.2.3

How to fix CVE-2020-37288

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2020-37288. EPSS is 0.35%. Act only if a listed version of Vyper: Return inside for is installed.

Which versions are affected?

Compare what you have installed with 0.1.0b10 → 0.2.3. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-670: Always-Incorrect Control Flow Implementation; CWE-691. EPSS 0.35%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 21, 2026 · NIST NVD

    Detected

    Vyper from 0.1.0b10 before 0.2.3 generates incorrect code for a return statement inside a for loop in an internal function called two or more internal calls deep, producing an invalid jump destination (stack underflow). Affected contracts revert such calls unnecessarily, which in limited circumstances could enable denial of service against public contracts.

  2. Oct 21, 2026 · NIST NVD

    Updated

    Vyper from 0.1.0b10 before 0.2.3 generates incorrect code for a return statement inside a for loop in an internal function called two or more internal calls deep, producing an invalid jump destination (stack underflow). Affected contracts revert such calls unnecessarily, which in limited circumstances could enable denial of service against public contracts.

  3. Oct 24, 2026 · GitHub Advisory Database

    Fix available

    vyper fixed in 0.2.3

  4. Oct 24, 2026 · GitHub Advisory Database

    Fix available

    vyper fixed in 0.2.3

  5. Oct 24, 2026 · GitHub Advisory Database

    Updated

    # 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 unles

Sources

  • CVE.orgVulnerability recordCVE-2020-37288

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2020-37288

    30-day exploitation probability 0.35%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-vg88-3v92-rjx2

    GitHub Advisory Database record mirrored by OSV.

    github.com
  • NIST NVDVulnerability recordCVE-2020-37288

    Vyper from 0.1.0b10 before 0.2.3 generates incorrect code for a return statement inside a for loop in an internal function called two or more internal calls deep, producing an invalid jump destination (stack underflow). Affected contracts revert such calls unnecessarily, which in

    nvd.nist.gov
  • OpenSSF OSV / OSV ScannerPackage advisoryGHSA-vg88-3v92-rjx2

    Vyper: Return inside for loop more than 1 level deep

    osv.dev
  • PyPA Advisory DatabasePackage advisoryGHSA-vg88-3v92-rjx2

    Vyper: Return inside for loop more than 1 level deep

    osv.dev

References

Freshness

Last verified in this catalog Oct 25, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • PyPA Advisory DatabaseOct 25, 2026
  • FIRST EPSSOct 25, 2026
  • GitHub Advisory DatabaseOct 24, 2026
  • OpenSSF OSV / OSV ScannerOct 24, 2026
  • CVE.orgOct 21, 2026
  • NIST NVDOct 21, 2026