Covert timing‑channel vulnerability in Legion of the Bouncy Castle Inc. BC‑JAVA core modules arises from non‑constant time comparisons performed during FrodoKEM operations. The flaw, categorized as CWE‑385, allows an adversary to extract private key material by measuring execution timings, thereby breaking the confidentiality of encrypted communications. The issue is confined to the core implementation of the FrodoKEM key‑encapsulation mechanism and does not affect other parts of the library.

The vulnerability impacts all BC‑JAVA core modules from version 2.17.3 up to, but not including, version 1.84. Users running these earlier releases are susceptible.

The CVSS score of 10 indicates a critical weakness. Although EPSS data is not available and the issue is not listed in the CISA KEV catalog, the nature of the flaw suggests that an attacker who can conduct precise timing measurements of the comparison routine could recover private keys. The attack vector is likely a side‑channel attack that requires the attacker to trigger or observe FrodoKEM comparisons, which may be feasible in environments where the application is exposed to an active network or on a shared hosting/platform that permits timing analysis.