CVE-2023-39363: Vyper incorrectly allocated named re-entrancy locks
Impact
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 either of the following vyper versions: 0.2.15, 0.2.16, 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) - A secondary function that utilizes the same key and would be affected by the improper state caused by the primary function
Patches https://github.com/vyperlang/vyper/pull/2439, https://github.com/vyperlang/vyper/pull/2514
Workarounds Upgrade to 0.3.1 or higher
References Technical post-mortem report: https://hackmd.io/@vyperlang/HJUgNMhs2
Other sources
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.
Affected Software
Remediation
Patch Available
Patch Available
Event History
Frequently Asked Questions
What is CVE-2023-39363?
CVE-2023-39363 is a vulnerability in Vyper, a Pythonic Smart Contract Language for the Ethereum Virtual Machine (EVM).
What is the impact of CVE-2023-39363?
CVE-2023-39363 allows for cross-function re-entrancy in contracts compiled with susceptible versions of Vyper, specifically 0.2.15, 0.2.16, and 0.3.0.
How can I fix CVE-2023-39363?
To fix CVE-2023-39363, update Vyper to version 0.3.1 or higher.
How severe is CVE-2023-39363?
CVE-2023-39363 has a severity value of 5.9, which is considered medium.
Where can I find more information about CVE-2023-39363?
You can find more information about CVE-2023-39363 on the GitHub pull requests [2439](https://github.com/vyperlang/vyper/pull/2439) and [2514](https://github.com/vyperlang/vyper/pull/2514), as well as the [security advisory](https://github.com/vyperlang/vyper/security/advisories/GHSA-5824-cm3x-3c38).