Vulnerability exploitation was spotted on April 24 by a blockchain security startup PeckShield. As a result, OKEx has suspended all ERC-20 tokens.
Vulnerable component: SmartMesh ERC20 token
CVSSv3 score: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L/E:H/RL:U/RC:C
CWE-ID: CWE-190 - Integer Overflow or Wraparound
The vulnerability allows a remote attacker to manipulate digital assets.
The vulnerability exists due to integer overflow in a smart contract implementation for SmartMesh (aka SMT) within Ethereum ERC20 token. A remote unauthenticated attacker can increase digital assets via crafted _fee and _value parameter.
Note: the vulnerability was actively exploited in April 2018 and was dubbed "proxyOverflow".