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Vulnerabilities

Security fix · CVE-2021-48019

VVE-2021-0002: Incorrect when using simple forwarder proxies deployed prior to EIP-1167 adoption

Published Apr 19, 2021 · catalog updated Oct 24, 2026 · VVE-2021-0002: Incorrect when using

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-2021-48019. EPSS is 0.25%. Act only if a listed version of VVE-2021-0002: Incorrect when using is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (VVE-2021-0002: Incorrect when using).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Low—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.25%
Remediation
Advisory link
Affected products
PyPI vyper

## Background @tjayrush reported a data handling issue with certain Web3 libraries using Vyper-deploy forwarder proxy contracts using our Vyper's built-in function prior to our change to support EIP-1167 style forwarder proxies. ### Impact If you are an end user of a forwarder-style proxy deployed using Vyper's built-in function AND you have a function that returns >4096 bytes AND you do no return data sanitation on the value returned, you could potentially see a data corruption issue. Otherwise, if you are handling the result of a return call AND you expect a specific that is less than 4096 (such as ) then the call will fail that check. ### Patches The issue was patched when we upgraded to EIP-1167 style forwarder proxies in #2281. ### Workarounds If you are making a call to a contract method that is expected to return <= 4096 bytes, there is no issue as the ABI decoders in both Solidity and Vyper will truncate the data properly. Web3 libraries will also do this, unless you are doing or directly. If you are using a Solidity library that checks of an external call to a forwarder proxy deployed prior to this patch, it will fail on that assertion (such as ). The workaround is to always do a greater than or equal to check, rather than a strict equals to check.

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 → 0.2.9

How to fix CVE-2021-48019

  • Upgrade

    CVE-2021-48019 lists a fix boundary at 0.2.9. Compare the installed build with that boundary before you change production.

  • Version check

    Fixed in 0.2.9

  • Advisory

    Open the cve_org record and follow its fix.

  • Official advisories

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-2021-48019. EPSS is 0.25%. Act only if a listed version of VVE-2021-0002: Incorrect when using is installed.

Which versions are affected?

Compare what you have installed with 0 → 0.2.9. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-20: Improper Input Validation. EPSS 0.25%. 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. Apr 19, 2021 · PyPA Advisory Database

    Detected

    ## Background @tjayrush reported a data handling issue with certain Web3 libraries using Vyper-deploy forwarder proxy contracts using our Vyper's built-in function prior to our change to support EIP-1167 style forwarder proxies. ### Impact If you are an end user of a forwarder-style proxy deployed using Vyper's built-in function AND you have a function that returns >4096 bytes AND you do no return

  2. Oct 24, 2026 · PyPA Advisory Database

    Fix available

    vyper fixed in 0.2.9

  3. Oct 24, 2026 · PyPA Advisory Database

    Fix available

    vyper fixed in 0.2.9

  4. Oct 24, 2026 · PyPA Advisory Database

    Updated

    ## Background @tjayrush reported a data handling issue with certain Web3 libraries using Vyper-deploy forwarder proxy contracts using our Vyper's built-in function prior to our change to support EIP-1167 style forwarder proxies. ### Impact If you are an end user of a forwarder-style proxy deployed using Vyper's built-in function AND you have a function that returns >4096 bytes AND you do no return

Sources

  • CVE.orgVulnerability recordCVE-2021-48019

    Official CVE identifier

    cve.org
  • PyPA Advisory DatabasePackage advisoryGHSA-375m-5fvv-xq23

    VVE-2021-0002: Incorrect when using simple forwarder proxies deployed prior to EIP-1167 adoption

    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.

  • CVE.orgOct 25, 2026
  • PyPA Advisory DatabaseOct 25, 2026