Cryptography / Predictable from Observable State

Web and API


Predictable from Observable State is a type of Cryptography vulnerability which is related to CWE-326 (Inadequate Encryption Strength). This vulnerability allows attackers to easily guess the encryption key and decipher the encrypted data, due to the use of weak encryption or weak entropy. It is also known as a “weak key” vulnerability. This type of vulnerability is commonly found in web and API applications, where encryption is used to protect sensitive data. (Reference: CWE directory and OWASP Testing Guide).


A Predictable from Observable State vulnerability can result in a severe breach of security, as attackers can decrypt encrypted data with relative ease. The risk assessment for this vulnerability is high, as attackers can use this vulnerability to gain access to sensitive data.


The best way to fix this vulnerability is to use strong encryption algorithms such as AES with a key length of at least 256 bits, and to use a secure random number generator to create strong entropy. Additionally, the encryption key should be stored securely.


The following code example is taken from the CVE directory and shows how an attacker could exploit a Predictable from Observable State vulnerability.

// Weakly encrypted data
String encryptedData = "EncryptedData";
String key = "abcdefghijklmnop";

// Decrypt the data
String decryptedData = decrypt(encryptedData, key);

// Print the decrypted data

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