In Botan 1.11.29 through 1.11.32, RSA decryption with certain padding options had a detectable timing channel which could given sufficient queries be used to recover plaintext, aka an "OAEP side channel" attack.

The Curve25519 code in botan before 1.11.31, on systems without a native 128-bit integer type, might allow attackers to have unspecified impact via vectors related to undefined behavior, as demonstrated on 32-bit ARM systems compiled by Clang.

The X509Certificate::allowedusage function in botan 1.11.x before 1.11.31 might allow attackers to have unspecified impact by leveraging a call with more than one KeyUsage set in the enum value.