CVE-2021-41121Network attack vector

Incorrect contract behavior via overwritten struct buffer

Published Oct 6, 2021 · Updated Aug 4, 2024

Memory corruption in Vyper before 0.3.0 allows attackers to alter compiled contract behavior via a function call inside a literal struct. During literal-struct construction, the compiler points the result at the current stack top, so an embedded private call reuses that memory and overwrites fields. Exposure requires bytecode compiled from a contract whose literal struct evaluates a function call; corrupted return data can change downstream contract logic.

CVSS severity8.8
High
EPSS probability1.07%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Vyper before 0.3.0 allows attackers to alter compiled contract behavior via a function call inside a literal struct. During literal-struct construction, the compiler points the result at the current stack top, so an embedded private call reuses that memory and overwrites fields. Exposure requires bytecode compiled from a contract whose literal struct evaluates a function call; corrupted return data can change downstream contract logic.

The record

CVE
CVE-2021-41121
Published
Oct 6, 2021
Updated
Aug 4, 2024
Vendor
Vyper
Product
Vyper
Classifications
CWE-119
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=< 0.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Vyper · Vyperversion=< 0.3.0

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer

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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