Contract bounds bypass via negative array indexes
Published Feb 7, 2024 · Updated Jun 17, 2025
Improper array-index validation in Vyper before 0.4.0 allows remote attackers to bypass contract array bounds via signed indexes. The type checker accepts int256 indexes for unsigned arrays, and code generation interprets negative values in two's complement, so sufficiently large arrays pass the runtime upper-bound check. Exploitation requires a contract compiled with an affected release, an attacker-controlled signed index, and an extremely large array; the result can expose invariant-protected elements or trigger unexpected contract behavior.
Summary
What happened
Improper array-index validation in Vyper before 0.4.0 allows remote attackers to bypass contract array bounds via signed indexes. The type checker accepts int256 indexes for unsigned arrays, and code generation interprets negative values in two's complement, so sufficiently large arrays pass the runtime upper-bound check. Exploitation requires a contract compiled with an affected release, an attacker-controlled signed index, and an extremely large array; the result can expose invariant-protected elements or trigger unexpected contract behavior.
The record
- CVE
- CVE-2024-24563
- Published
- Feb 7, 2024
- Updated
- Jun 17, 2025
- Vendor
- Vyper
- Product
- Vyper
- Classifications
- CWE-129
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 7, 2024CVE publishedPublication date reported by the CVE source.
- Jun 17, 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.
- Affected versionversion=<= 0.3.10
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Negative array index bounds-check bypass PoCproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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