75%
39%
60%
The "PayWinner" function of a simplelottery smart contract implementation for The Ethereum Lottery, an Ethereum gambling game, generates a random value with publicly readable variable "maxTickets" (which is private, yet predictable and readable by the eth.getStorageAt function). Therefore, it allows attackers to always win and get rewards.
The "PayWinner" function of a simplelottery smart contract implementation for The Ethereum Lottery, an Ethereum gambling game, generates a random value with publicly readable variable "maxTickets" (which is private, yet predictable and readable by the eth.getStorageAt function). Therefore, it allows attackers to always win and get rewards.
CVSS 3.1 Base Score 7.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
CVSS 2.0 Base Score 5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (AV:N/AC:L/Au:N/C:P/I:N/A:N).
Both of these examples use a statistical PRNG to generate a random number:
int accountID = random.nextInt();
int randNum = rand();The random number functions used in these examples, rand() and Random.nextInt(), are not considered cryptographically strong. An attacker may be able to predict the random numbers generated by these functions. Note that these example also exhibit CWE-337 (Predictable Seed in PRNG).
ExploitPedia is constantly evolving. Sign up to receive a notification when we release additional functionality.
If you'd like to report a bug or have any suggestions for improvements then please do get in touch with us using this form. We will get back to you as soon as we can.