Vulnerability · Published Oct 21, 2026 · Assigned by VulnCheck

CVE-2021-48020Vyper before 0.3.0 Memory Corruption via Internal Function Calls in Arrays

Medium 6.5

In plain English

A medium-severity out-of-bounds write in vyper from vyperlang. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.3%top 79.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Vyper from 0.1.0b4 before 0.3.0 contains a memory corruption vulnerability caused by an incorrect stack tip pointer when internal function calls are performed inside arrays. Contracts placing internal calls in nested array elements, external call arguments, struct literals, or raw_log topics can have memory corrupted, producing incorrect contract behavior.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	vyper	0.2.12	GHSA-22wc-c9wj-6q2v

Affected products (as reported)

Vendor	Product	Versions
vyperlang	vyper	0.1.0b4 – before 0.3.0

Weakness: CWE-787 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L

References

GitHub Security Advisory (GHSA-22wc-c9wj-6q2v) vendor-advisory
VulnCheck Advisory: Vyper before 0.3.0 Memory Corruption via Internal Function Calls in Arrays third-party-advisory