Cloak’s AES‑CTR cipher lacks integrity protection; the decrypt routine only checks the key tag and length, which is a weakness classified as CWE‑649. This allows an attacker who can modify stored ciphertext to flip bits and cause the library to output any chosen plaintext. The attacker can therefore forge tokens, credentials, or any encrypted data that the application relies on.

The flaw affects every release of danielberkompas Cloak from version 0.1.0‑pre onward. All deployments that configure the vault to use Cloak.Ciphers.AES.CTR or the deprecated Cloak.Ciphers.Deprecated.AES.CTR are susceptible.

With a CVSS score of 8.2, the vulnerability is high severity. The EPSS score of less than 1% indicates a very low current exploitation probability, and the vulnerability is not listed in CISA’s KEV catalog. The attack requires write access to the encrypted store, which can be obtained via SQL injection, a compromised database replica, or direct file manipulation. Once obtain such access, the attacker can modify any ciphertext of the target length, causing the application to decrypt it to attacker‑chosen data, thereby compromising data integrity and potentially undermining authentication or authorization mechanisms.