# CVE-2023-40014: OpenZeppelin Contracts improper escaping in ERC2771Context

Source: https://junglewise.ai/threats/cve-2023-40014-openzeppelin-contracts-improper-escaping-in-erc2771context  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2023-08-11. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2023-40014 · Severity: low · CVSS 3.1 · Published 2023-08-11

OpenZeppelin Contracts is a widely-used library for building secure smart contracts on blockchain networks. When using the ERC2771Context module with a custom trusted forwarder, a logic flaw can cause the sender address to be incorrectly resolved as zero in certain conditions, potentially leading to authentication bypass or authorization failures in dependent applications.

Technologies: [@openzeppelin/contracts (npm)](https://junglewise.ai/threats/technologies/openzeppelin-contracts), [@openzeppelin/contracts-upgradeable (npm)](https://junglewise.ai/threats/technologies/openzeppelin-contracts-upgradeable), [OpenZeppelin Contracts](https://junglewise.ai/threats/technologies/contracts), [OpenZeppelin Contracts Upgradeable](https://junglewise.ai/threats/technologies/contracts-upgradeable). Vendors: [npm](https://junglewise.ai/threats/vendors/npm), [OpenZeppelin](https://junglewise.ai/threats/vendors/openzeppelin).

## Quick answers

**Is CVE-2023-40014 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2023-40014 being exploited in the wild.

**How severe is CVE-2023-40014?** Low severity, with a CVSS score of 3.1, published 11 August 2023.

**Which products and versions are affected?** @openzeppelin/contracts (npm) SEMVER:introduced=4.0.0,fixed=4.9.3; @openzeppelin/contracts-upgradeable (npm) SEMVER:introduced=4.0.0,fixed=4.9.3; OpenZeppelin Contracts >=4.0.0 to <4.9.3; OpenZeppelin Contracts Upgradeable >=4.0.0 to <4.9.3.

**Is there a fix for CVE-2023-40014?** Yes. @openzeppelin/contracts (npm): upgrade to 4.9.3 or later; @openzeppelin/contracts-upgradeable (npm): upgrade to 4.9.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2023-40014 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2023-40014?** Check whether you run @openzeppelin/contracts (npm), @openzeppelin/contracts-upgradeable (npm), OpenZeppelin Contracts or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @openzeppelin/contracts (npm): upgrade to 4.9.3 or later

  ```sh
  npm install @openzeppelin/contracts@4.9.3
  ```

- @openzeppelin/contracts-upgradeable (npm): upgrade to 4.9.3 or later

  ```sh
  npm install @openzeppelin/contracts-upgradeable@4.9.3
  ```


## Technical details

The vulnerability exists in ERC2771Context (versions 4.0.0 through 4.9.2) and stems from improper escaping or validation of calldata when extracting the message sender from a trusted forwarder. When a custom forwarder initiates a call with calldata shorter than 20 bytes, the _msgSender() function may incorrectly return address(0) instead of the legitimate sender address. This is classified as CWE-116 (Improper Encoding or Escaping of Output). The issue requires use of a non-standard forwarder implementation; OpenZeppelin's own MinimalForwarder and known production forwarders are unaffected. The vulnerability was patched in version 4.9.3.

## Affected products

- OpenZeppelin Contracts >=4.0.0 to <4.9.3
- OpenZeppelin Contracts Upgradeable >=4.0.0 to <4.9.3

## Identifiers

- CVE-2023-40014
- GHSA-g4vp-m682-qqmp

## Timeline

- 2023-08-10: disclosed: Vulnerability publicly disclosed
- 2023-08-11: patched: Patch released in version 4.9.3

## References

- [https://github.com/OpenZeppelin/openzeppelin-contracts/security/advisories/GHSA-g4vp-m682-qqmp](https://github.com/OpenZeppelin/openzeppelin-contracts/security/advisories/GHSA-g4vp-m682-qqmp)

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