A flaw in the Legion of the Bouncy Castle Inc. BC-LTS library on Linux for x86_64, AVX, and AVX-512f causes a BadTagException when GCM decryption is performed in chunked mode at certain boundaries. The failure can abort decryption and disrupt any service that relies on the library to process ciphertext, effectively causing a denial‑of‑service condition. The issue is present in the gcm128w and gcm512w modules, and 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‑LTS component, version 2.73.0 through 2.73.10, 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 the EPSS score is less than 1%, while it is not listed in the CISA KEV catalog. Exploitation requires an attacker to supply crafted, chunked ciphertext to an application that uses BC‑LTS for decryption; this can occur when the 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.