CVE-2026-5598

A flaw was found in Legion of the Bouncy Castle Inc. BC-JAVA core. A covert timing channel vulnerability, caused by non-constant time comparisons, risks the leakage of private keys in the FrodoKEM implementation. An unauthenticated, remote attacker can potentially exploit this timing discrepancy to gain unauthorized access to sensitive cryptographic information.

To exploit this issue, an unauthenticated attacker needs to send highly specific, malformed ciphertexts to the target server. These payloads are used to interact with the private key of the server in a way that the vulnerable, non-constant time code paths are triggered during the verification step. An attack typically requires sending a large volume of these requests to perform statistical analysis on the resulting timing variations, increasing its complexity. The primary security impact of this vulnerability is the potential leakage of private keys associated with the FrodoKEM implementation. This can compromise encrypted communications or authentication mechanisms.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this vulnerability, implement aggressive rate limiting and anomaly detection, specifically looking for unusual, high-frequency cryptographic handshake failures or anomalous traffic patterns targeting endpoints that handle key exchanges in the network logs.