CVE-2023-40014Network attack vector

Caller misidentification via short forwarded calldata

Published Aug 10, 2023 · Updated Oct 3, 2024

Incorrect caller identification in OpenZeppelin Contracts 4.0.0 through 4.9.2 allows attackers to make _msgSender return address(0). ERC2771Context._msgSender treats every call from a trusted forwarder as containing a 20-byte signer suffix, so subtracting 20 from shorter calldata underflows and the assembly calldata load resolves to address(0). Reachability requires a custom trusted forwarder that emits sub-20-byte calldata; downstream impact depends on how the consuming contract uses caller identity.

CVSS severity5.3
Medium
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect caller identification in OpenZeppelin Contracts 4.0.0 through 4.9.2 allows attackers to make _msgSender return address(0). ERC2771Context._msgSender treats every call from a trusted forwarder as containing a 20-byte signer suffix, so subtracting 20 from shorter calldata underflows and the assembly calldata load resolves to address(0). Reachability requires a custom trusted forwarder that emits sub-20-byte calldata; downstream impact depends on how the consuming contract uses caller identity.

The record

CVE
CVE-2023-40014
Published
Aug 10, 2023
Updated
Oct 3, 2024
Vendor
OpenZeppelin
Product
OpenZeppelin Contracts
Classifications
CWE-116, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.0.0, < 4.9.3
  2. Affected versionversion=4.0.0 <4.9.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenZeppelin · OpenZeppelin Contractsversion=>= 4.0.0, < 4.9.3; version=4.0.0 <4.9.3

Published CVSS scores

5.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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