The vulnerability in the Botan cryptography library occurs during SM2 decryption. A check that verifies the size of the authentication code (C3) is omitted, so an attacker can supply a ciphertext that is too short and force the library to read beyond the intended buffer. This heap over‑read can reach 31 bytes and results in a crash or other undefined behavior, potentially producing a denial‑of‑service effect.

All releases of Botan from version 2.3.0 up to, but not including, 3.11.0 are affected. The vulnerability appears in the SM2 decryption routine used by any application that links to the library.

The CVSS score of 8.2 signals high severity. The EPSS score is less than 1 % and the vulnerability is not listed in CISA’s KEV catalog. A successful exploitation requires an attacker to supply a malformed SM2 ciphertext to a component that uses Botan for decryption. The impact is limited to an application crash or other undefined behavior; no direct privilege escalation or data compromise is described in the advisory.