GHSA-gr7h-xw4f-wh86: 
Java vulnerability analysis and mitigation

A security vulnerability was identified in Sakai's kernel-impl component (GHSA-gr7h-xw4f-wh86) affecting versions up to 23.3. The issue involves the use of a predictable Pseudo-Random Number Generator (PRNG) in the EncryptionUtilityServiceImpl class for generating server-side encryption keys. The vulnerability was discovered by Suraj Gangwar and patched by Sam Ottenhoff from Longsight, with fixes implemented in Sakai versions 23.5, 25.0, and trunk (GitHub Advisory).

The vulnerability stems from the EncryptionUtilityServiceImpl's initialization of an AES256TextEncryptor password (serverSecretKey) using RandomStringUtils with the default java.util.Random. This implementation is problematic as java.util.Random is a non-cryptographic PRNG that can be predicted from limited state/seed information, such as start time windows. The vulnerability has been assigned a CVSS score of 5.9 (Moderate) with the vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N, indicating network attack vector with high complexity, no privileges required, and potential impact on confidentiality (GitHub Advisory).

The vulnerability significantly reduces the effective search space of the generated encryption key. An attacker who can obtain ciphertexts (such as exported or at-rest strings protected by this service) and approximate the PRNG seed could potentially reconstruct the serverSecretKey and decrypt affected data (GitHub Advisory).

The vulnerability has been addressed in SAK-49866 and is patched in Sakai versions 23.5, 25.0, and trunk. Users are advised to upgrade to these patched versions to mitigate the vulnerability (GitHub Advisory).