CVE-2023-46232: era-compiler-vyper First Immutable Variable Initialization vulnerability

Vulnerability summary

CVE-2023-46232 is a medium (CVSS 5.3) vulnerability in matter-labs era-compiler-vyper. EPSS estimates a 0.69% chance of exploitation in the next 30 days, higher than 52.9% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 25-10-2023
   PublishedVulnerability first disclosed.
2. 10-09-2024
   Last modifiedVulnerability information updated.

Description

era-compiler-vyper is the EraVM Vyper compiler for zkSync Era, a layer 2 rollup that uses zero-knowledge proofs to scale Ethereum. Prior to era-compiler-vype version 1.3.10, a bug prevented the initialization of the first immutable variable for Vyper contracts meeting certain criteria. The problem arises when there is a String or Array with more 256-bit words allocated than initialized. It results in the second word’s index unset, that is effectively set to 0, so the first immutable value with the actual 0 index is overwritten in the ImmutableSimulator. Version 1.3.10 fixes this issue by setting all indexes in advance. The problem will go away, but it will get more expensive if the user allocates a lot of uninitialized space, e.g. `String[4096]`. Upgrading and redeploying affected contracts is the only way of working around the issue.

• CWE-471Modification of Assumed-Immutable Data (MAID)The product does not properly protect an assumed-immutable element from being modified by an attacker.