In the Bouncy Castle Java library before version 1.86, the NTRU cryptographic routine reduced secret polynomial values by using the % operator, which the compiler turned into an integer division whose latency depends on the secret operand. This non‑constant‑time operation creates a measurable timing side channel that an attacker can exploit to recover information about the private key, exposing confidentiality of all data protected by that key. The weakness is classified as CWE‑208.

The vulnerability affects the Bouncy Castle Java cryptography library (BC‑JAVA) on all versions prior to 1.86, specifically the NTRU implementation used during key generation, encapsulation, and decapsulation. Any application that imports this library and performs these operations is potentially exposed.

The CVSS score of 8.2 indicates a high impact on confidentiality. The EPSS score is not available, and the vulnerability is not listed in the CISA KEV catalog, suggesting that a public exploit has not yet been documented. However, the attack vector requires precise timing measurements, which is feasible for an adversary with direct or controlled access to the system’s execution environment. Successful exploitation would allow the attacker to recover the private key and compromise all cryptographic functions relying on it.