Contract semantic corruption via undersized concat buffer
Published Jan 18, 2024 · Updated Jun 2, 2025
Out-of-bounds writes in Vyper before 0.4.0 allow attackers to alter compiled smart-contract semantics through crafted concat usage. The concat build_IR allocates only the declared data buffer, but copy_bytes can copy a padded 32-byte word past its end and overwrite adjacent EVM memory. Reachability requires length-dependent concat use in an internal function near its return, where later allocations do not absorb the overrun; the published contract search found no vulnerable production contracts.
Summary
What happened
Out-of-bounds writes in Vyper before 0.4.0 allow attackers to alter compiled smart-contract semantics through crafted concat usage. The concat build_IR allocates only the declared data buffer, but copy_bytes can copy a padded 32-byte word past its end and overwrite adjacent EVM memory. Reachability requires length-dependent concat use in an internal function near its return, where later allocations do not absorb the overrun; the published contract search found no vulnerable production contracts.
The record
- CVE
- CVE-2024-22419
- Published
- Jan 18, 2024
- Updated
- Jun 2, 2025
- Vendor
- Vyper
- Product
- Vyper
- Classifications
- CWE-120, CWE-787
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 18, 2024CVE publishedPublication date reported by the CVE source.
- Jun 2, 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=< 0.4.0
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
- Upstream concat buffer-overflow proof of conceptproof of concept · demonstrated
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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