A flaw was found in Botan 1.11.32 through 2.x before 2.6.0. An off-by-one error when processing malformed TLS-CBC ciphertext could cause the receiving side to include in the HMAC computation exactly 64K bytes of data following the record buffer, aka an over-read. The MAC comparison will subsequently fail and the connection will be closed. This could be used for denial of service. No information leak occurs. Reference: https://botan.randombit.net/security.html
In the botan package, we only package stable 1.X versions up to and including 1.10. The botan2 package contains stable 2.X versions. Moreover, 2.6.0 is already in rawhide, and in testing for F27 and F28.