CVE-2024-45056: `fold (xor (shl 1, x), -1) -> (rotl ~1, x)` misoptimization in zksolc

Vulnerability summary

CVE-2024-45056 is a medium (CVSS 5.9) Incorrect Calculation vulnerability in matter-labs era-compiler-solidity. EPSS estimates a 0.40% chance of exploitation in the next 30 days, higher than 34.6% of scored vulnerabilities.

Timeline

1. 29-08-2024
   PublishedVulnerability first disclosed.
2. 29-08-2024
   Last modifiedVulnerability information updated.

Description

zksolc is a Solidity compiler for ZKsync. All LLVM versions since 2015 fold `(xor (shl 1, x), -1)` to `(rotl ~1, x)` if run with optimizations enabled. Here `~1` is generated as an unsigned 64 bits number (`2^64-1`). This number is zero-extended to 256 bits on EraVM target while it should have been sign-extended. Thus instead of producing `roti 2^256 - 1, x` the compiler produces `rotl 2^64 - 1, x`. Analysis has shown that no contracts were affected by the date of publishing this advisory. This issue has been addressed in version 1.5.3. Users are advised to upgrade and redeploy all contracts. There are no known workarounds for this vulnerability.

• CWE-682Incorrect CalculationThe product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.