CVE-2023-39363

What it is

Vyper is a Pythonic Smart Contract Language for the Ethereum Virtual Machine (EVM). In versions 0.2.15, 0.2.16 and 0.3.0, named re-entrancy locks are allocated incorrectly. Each function using a named re-entrancy lock gets a unique lock regardless of the key, allowing cross-function re-entrancy in contracts compiled with the susceptible versions. A specific set of conditions is required to result in misbehavior of affected contracts, specifically: a `.vy` contract compiled with `vyper` versions `0.2.15`, `0.2.16`, or `0.3.0`; a primary function that utilizes the `@nonreentrant` decorator with a specific `key` and does not strictly follow the check-effects-interaction pattern (i.e. contains an external call to an untrusted party before storage updates); and a secondary function that utilizes the same `key` and would be affected by the improper state caused by the primary function. Version 0.3.1 contains a fix for this issue.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data tampering, service disruption.

Exploit odds

0.8% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2023-08-07 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 06:12 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.8% in the next 30 days (EPSS).
• Severity: 9.1 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2023-08-07 19:15 UTC

Last modified

2026-06-17 06:12 UTC

Exploit probability

0.8% · EPSS, next 30 days

Weakness

CWE-863 · Incorrect authorization

Record status

Modified

Affected

• Vyperlang Vyper 0.2.15
• Vyperlang Vyper 0.2.16
• Vyperlang Vyper 0.3.0

Attack profile CVSS 4.0 · 9.1

Attack vector

Network

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

None

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2023-39363.md and follow it. Check whether this project is affected by CVE-2023-39363. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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