CVE-2023-28431
Assigner: GitHub_M
Published: 2023-03-22T20:11:43.772Z
State: PUBLISHED
title: Frontier's modexp precompile is slow for even modulus
problemTypes: descriptions: cweId: CWE-682
description: CWE-682: Incorrect Calculation
type: CWE
metrics: cvssV3_1: attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 7.5
baseSeverity: HIGH
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
version: 3.1
affected: vendor: paritytech
product: frontier
versions: version: <= 0.1.0
status: affected
descriptions: value: Frontier is an Ethereum compatibility layer for Substrate. Frontier's `modexp` precompile uses `num-bigint` crate under the hood. In the implementation prior to pull request 1017, the cases for modulus being even and modulus being odd are treated separately. Odd modulus uses the fast Montgomery multiplication, and even modulus uses the slow plain power algorithm. This gas cost discrepancy was not accounted for in the `modexp` precompile, leading to possible denial of service attacks.

No fixes for `num-bigint` are currently available, and thus this issue is fixed in the short term by raising the gas costs for even modulus, and in the long term fixing it in `num-bigint` or switching to another modexp implementation. The short-term fix for Frontier is deployed at pull request 1017. There are no known workarounds aside from applying the fix.
source: advisory: GHSA-fcmm-54jp-7vf6
discovery: UNKNOWN