Big-Tech-Sux

**Name of the Vulnerable Software and Affected Versions** Vyper versions 0.2.15 through 0.3.0 **Description** The issue arises from the incorrect allocation of named re-entrancy locks in Vyper versions 0.2.15, 0.2.16, and 0.3.0. 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. **Recommendations** To resolve the issue, upgrade to Vyper version 0.3.1 or higher. As a temporary workaround, consider restricting the use of the `@nonreentrant` decorator with specific keys across multiple functions to minimize the risk of cross-function re-entrancy. Avoid using the same `key` in the `@nonreentrant` decorator across multiple functions until the issue is resolved.