Vulnerability · Published Oct 21, 2026 · Assigned by VulnCheck

CVE-2026-114114Vyper through 0.5.0b1 Literal Value Substitution via Multi-byte Characters

Medium 5.3

In plain English

A medium-severity security flaw in vyper from vyperlang. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities).

Severity (CVSS 3.1)5.3Medium

Exploit odds (30 days)0.3%top 82.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Vyper 0.1.0b1 before 0.1.0b12, 0.1.0b14, and 0.4.1 through 0.5.0b1 mix character-based line offsets with Python's UTF-8 byte col_offset values in vyper/ast/parse.py, so multi-byte characters shift the source slices used to reconstruct later numeric literals. An attacker contributing source with non-ASCII identifiers that NFKC-normalize to ASCII, or an invisible byte-order mark, can silently substitute addresses, integers or other constants in compiled code.

Affected products (as reported)

Vendor	Product	Versions
vyperlang	vyper	0.1.0b1 – before 0.1.0b12
vyperlang	vyper	0.1.0b14 – before 0.1.0b15
vyperlang	vyper	0.4.1 – through 0.5.0b1

Weakness: CWE-176 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

References

GitHub Security Advisory (GHSA-r3c7-7xwm-6vfw) vendor-advisory
VulnCheck Advisory: Vyper through 0.5.0b1 Literal Value Substitution via Multi-byte Characters third-party-advisory