This is the report from a security audit performed on BNB Token by gorbunovperm.
Audit of Top 200 CoinMarketCap tokens.
In total, 4 issues were reported including:
-
0 high severity issue.
-
0 medium severity issues.
-
4 low severity issues.
-
0 minor observations.
-
It is possible to double withdrawal attack. More details here
-
Lack of transaction handling mechanism issue. WARNING! This is a very common issue and it already caused millions of dollars losses for lots of token users! More details here
Add into a function transfer(address _to, ... )
following code:
require( _to != address(this) );
-
According to ERC20 standard when coins are minted a
Transfer
event should be emitted. -
There is no
Approval
event call atapprove
function. And EIP20 says:
MUST trigger on any successful call to approve(address _spender, uint256 _value).
- The
burn
function also should emit theTransfer
event.
EIP20 says that:
Transfers of 0 values MUST be treated as normal transfers and fire the Transfer event. But in this contract, function
transfer
has a condition:
if (_value <= 0) throw;
- There is no way to reset approved value to 0, because
approve
function contains:
if (_value <= 0) throw;
- Also it breaks the EIP20 security recommendation:
To prevent attack vectors like the one described here and discussed here, clients SHOULD make sure to create user interfaces in such a way that they set the allowance first to 0 before setting it to another value for the same spender. THOUGH The contract itself shouldn't enforce it, to allow backwards compatibility with contracts deployed before
There are some vulnerabilities were discovered in this contract.