Headline
CVE-2023-39363: Incorrectly allocated named re-entrancy locks
Vyer 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.
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
#2439, #2514
Workarounds
Upgrade to 0.3.1 or higher
References
Technical post-mortem report: https://hackmd.io/@vyperlang/HJUgNMhs2
Related news
### 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 ### Refe...