Information Disclosure in SiYuan Kernel Enabling Offline Password Cracking

SiYuan kernel versions prior to 0.0.0-20260724102025-3bc014c7dc32 contain an information disclosure vulnerability (CVE-2026-72801) affecting the handling of encrypted notebook configuration metadata. Specifically, two API endpoints, /api/system/getConf and /api/notebook/getNotebookConf, fail to properly redact sensitive cryptographic material when accessed by non-administrator roles.

An unauthenticated remote attacker or an unauthorized publish reader can retrieve the Argon2id salt, key derivation function (KDF) parameters, and master password verifiers (KEKVerifier/KEKMAC). Furthermore, the attacker can obtain the wrapped per-notebook data encryption key (WrappedDEK). Because these endpoints do not implement rate limiting or server-side auditing of guesses, an attacker can perform high-speed offline GPU cracking of the master password. Once the master password is recovered, the attacker uses the retrieved wrapped data key to decrypt notebook content. This vulnerability moves the threat of an offline filesystem attack to a remote, network-accessible pre-authentication exploitation vector.

Attack Chain

1. Attacker identifies a SiYuan instance with publish mode enabled (default port 6808).
2. Attacker interacts with the /api/system/getConf endpoint using a low-privilege RoleReader token or as an anonymous reader if Publish.Auth.Enable is set to false.
3. The server erroneously returns the NotebookCrypto object, providing the attacker with the MasterSalt, KDFParams, KEKVerifier, and KEKMAC.
4. Attacker calls /api/notebook/getNotebookConf with a target notebook_id to retrieve the BoxCrypt.WrappedDEK and WrapNonce.
5. Attacker performs offline brute-force or dictionary attacks against the Argon2id KDF parameters using locally managed GPU clusters.
6. Successful password recovery derives the Key Encryption Key (KEK).
7. Attacker decrypts the WrappedDEK to obtain the notebook's master Data Encryption Key (DEK).
8. Attacker uses the DEK to decrypt the target notebook files, resulting in full data compromise.

Impact

The vulnerability allows unauthorized remote parties to bypass the security of encrypted notebooks. Since the attack occurs entirely offline using retrieved parameters, it cannot be detected or blocked by server-side intrusion prevention systems. A successful attack results in the total loss of confidentiality for all notebooks stored within the compromised SiYuan instance.

Recommendation

Prioritize patching the SiYuan kernel to version 0.0.0-20260724102025-3bc014c7dc32 or later. Ensure that the HideConfSecret function correctly excludes all NotebookCrypto fields for non-administrator roles, and verify that reader role filtering is enforced across all BoxCrypt related endpoints. Monitor web access logs for high-frequency POST requests to /api/system/getConf and /api/notebook/getNotebookConf originating from unauthorized or anonymous user agents.