CVE-2025-47285Public exploitNetwork attack vector

Incorrect contract behavior via skipped concat side effects

Published May 15, 2025 · Updated May 15, 2025

Incorrect code generation in Vyper 0.4.2rc1 and earlier allows attackers to trigger contracts that omit intended side effects. The concat() code-generation fast path ignores an argument whenever its maximum length is zero, so the argument expression is never evaluated. Triggering the affected bytecode requires a contract compiled from a zero-length bytestring ternary expression with a side effect; calls to that contract can silently omit intended state changes.

CVSS severityUnavailable
Unscored
EPSS probability0.44%
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 0.4.2rc1 and earlier allows attackers to trigger contracts that omit intended side effects. The concat() code-generation fast path ignores an argument whenever its maximum length is zero, so the argument expression is never evaluated. Triggering the affected bytecode requires a contract compiled from a zero-length bytestring ternary expression with a side effect; calls to that contract can silently omit intended state changes.

The record

CVE
CVE-2025-47285
Published
May 15, 2025
Updated
May 15, 2025
Vendor
Vyper
Product
Vyper
Classifications
CWE-691
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 15, 2025CVE publishedPublication date reported by the CVE source.
  2. May 15, 2025Record 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=<= 0.4.2rc1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vyper · Vyperversion=<= 0.4.2rc1

Published CVSS scores

2.9GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

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 exploitPublished

Weakness, pattern, technique

CWE-691Insufficient Control Flow Management

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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