CWE-338

The fallback function of a simple lottery smart contract implementation for Lucky9io, an Ethereum gambling game, generates a random value with the publicly readable variable entry_number. This variable is private, yet it is readable by eth.getStorageAt function. Also, attackers can purchase a ticket at a low price by directly calling the fallback function with small msg.value, because the developer set the currency unit incorrectly. Therefore, it allows attackers to always win and get rewards.

Lightbend Akka 2.5.x before 2.5.16 allows message disclosure and modification because of an RNG error. A random number generator is used in Akka Remoting for TLS (both classic and Artery Remoting). Akka allows configuration of custom random number generators. For historical reasons, Akka included the AES128CounterSecureRNG and AES256CounterSecureRNG random number generators. The implementations had a bug that caused the generated numbers to be repeated after only a few bytes. The custom RNG implementations were not configured by default but examples in the documentation showed (and therefore implicitly recommended) using the custom ones. This can be used by an attacker to compromise the communication if these random number generators are enabled in configuration. It would be possible to eavesdrop, replay, or modify the messages sent with Akka Remoting/Cluster.

Pivotal CredHub Service Broker, versions prior to 1.1.0, uses a guessable form of random number generation in creating service broker’s UAA client. A remote malicious user may guess the client secret and obtain or modify credentials for users of the CredHub Service.

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 endCoinFlip function and throwSlammer function of the smart contract implementations for Cryptogs, an Ethereum game, generate random numbers with an old block’s hash. Therefore, attackers can predict the random number and always win the game.

The random() function of the smart contract implementation for CryptoSaga, an Ethereum game, generates a random value with publicly readable variables such as timestamp, the current block’s blockhash, and a private variable (which can be read with a getStorageAt call). Therefore, attackers can precompute the random number and manipulate the game (e.g., get powerful characters or get critical damages).