The GOST 28147-2015 CTR mode implementation (G3413CTRBlockCipher) in the Legion of the Bouncy Castle BC-JAVA bcprov core module only increments the final byte of the counter, so the counter wraps after 255 blocks and the keystream is reused. Reusing CTR keystream allows an attacker who can observe two ciphertexts produced with the same key/IV to recover the XOR of the plaintexts, breaking confidentiality. Affects BC-JAVA from 1.59 before 1.84 (with backported fixes in 1.80.2 and 1.81.1).
// cvss v3.1 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None
Checked 2026-09-25 at 17:59 UTC. The most recent advisory here was published 2026-04-17. Updated continuously from NVD, GHSA, OSV and CNA feeds.