A flaw in the Legion of the Bouncy Castle Inc. BC-FJA library causes a BadTagException when GCM decryption is performed in chunked mode at certain boundaries. The failure can terminate decryption and disrupt any service that relies on the library to process ciphertext, effectively causing a denial‑of‑service condition. The underlying weakness is reflected in CWE‑1068, indicating that externally controlled input can influence internal pointer logic during authentication tag verification.

The issue affects the BC‑FJA component, version 2.1.0 through 2.1.2, running on Linux x86_64 with AVX or AVX‑512f instruction sets. The problematic modules are gcm128w and gcm512w within that library.

The CVSS score is 5.1, indicating moderate severity, and no EPSS data is available; it is not listed in the CISA KEV catalog. Exploitation requires an attacker to supply crafted, chunked ciphertext to an application that uses BC‑FJA for decryption; this can occur when an attacker can pass input to the decryption API, such as via a network service or any component that processes untrusted data. The impact is primarily availability, as the decryption failure terminates the operation and may disrupt dependent services.