CVE-2023-40015Public exploitNetwork attack vector

Incorrect contract execution via reversed operand evaluation

Published Sep 4, 2023 · Updated Nov 19, 2024

Incorrect code generation in Vyper 0.4.0 and earlier allows remote attackers to alter contract behavior through affected expressions. The compiler evaluates operands right to left in specified built-ins and operators, so a state-changing operand can precede a dependent read and generate unintended semantics. Exploitation requires a contract compiled by an affected release to use one of those expressions with interdependent side effects; invoking that path can change contract state or results.

CVSS severity3.7
Low
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect code generation in Vyper 0.4.0 and earlier allows remote attackers to alter contract behavior through affected expressions. The compiler evaluates operands right to left in specified built-ins and operators, so a state-changing operand can precede a dependent read and generate unintended semantics. Exploitation requires a contract compiled by an affected release to use one of those expressions with interdependent side effects; invoking that path can change contract state or results.

The record

CVE
CVE-2023-40015
Published
Sep 4, 2023
Updated
Nov 19, 2024
Vendor
Vyper
Product
Vyper
Classifications
CWE-670
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 4, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 19, 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=<= 0.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vyper · Vyperversion=<= 0.4.0

Published CVSS scores

3.7GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
5.3NIST NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-670Always-Incorrect Control Flow Implementation

Public exploit references

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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