Summary
When PAM (dialog) authentication is used, the connector can be coerced into sending the account password in cleartext over an insecure connection. A hostile or man-in-the-middle server can trigger this with the default configuration, disclosing the user's password.
Details
The mysqlclearpassword plugin is gated behind a secure connection: the driver refuses to transmit the password in cleartext over plain TCP. The sibling PAM plugin handler (SendPamAuthPacketFactory, server-side plugin name dialog) did not override that gate and inherited the default value false, so it was not subject to the same secure-transport requirement.
As a result, a hostile or man-in-the-middle server can issue an Authentication Switch Request for the dialog plugin over plain TCP, and the driver responds with the user's password in cleartext. With the default configuration (sslMode=DISABLE, restrictedAuth=null) this is reachable with no non-default options.
Am I affected?
You are affected if all of the following hold:
You use mariadb Connector/J at a version below the patched release(s). Connections can occur over an insecure transport — i.e. plain TCP (sslMode=DISABLE), or a TLS mode that establishes server identity only via self-signed-certificate fingerprint validation. An attacker can occupy an on-path (MITM) position, or otherwise cause the client to connect to a server they control, and present an Authentication Switch Request for the dialog plugin.
Connections over properly verified TLS or a local Unix socket are not exposed to this vector.
Impact
Disclosure of the authenticating account's password in cleartext to an on-path or hostile server. The captured credentials can then be reused to authenticate to the database.
Patches
Fixed in 2.7.14, 3.3.5, 3.4.3, and 3.5.9. Upgrade to the patched release on your branch (3.5.x → 3.5.9, 3.4.x → 3.4.3, 3.0/3.1/3.2/3.3.x → 3.3.5, 2.x → 2.7.14). PAM (dialog) is now treated exactly like mysqlclearpassword: it may only run over a secure transport. SendPamAuthPacketFactory overrides the secure-required flag to true, and the authentication dispatcher permits a secure-required plugin only when the connection is TLS or a local Unix socket. The pre-existing check that blocks non-MITM-proof plugins when server identity relies solely on self-signed-certificate fingerprint validation continues to apply. Net effect: PAM is allowed over TLS or a Unix socket, and rejected over plain TCP or fingerprint-only connections.
Workarounds
If you cannot upgrade immediately:
Connect over verified TLS (set sslMode=verify-full) so a man-in-the-middle cannot impersonate the server, or use a local Unix socket. Restrict the permitted authentication plugins via restrictedAuth so dialog cannot be negotiated over an insecure transport.
Credit
Reported by Yalguun Tumenkhuu (@fg0x0).
Summary
The connector encodes and decodes all character data assuming the connection character set is UTF-8. A server can change charactersetclient mid-session to a non-UTF-8 charset, after which the driver and server interpret the same bytes under different encodings, causing silent data corruption and a client/server charset-confusion mismatch.
Details
The driver encodes and decodes all character data on the assumption that the connection character set is UTF-8. Charset can be changed by commands like SET NAMES... commands.
If the new charset is not UTF-8, the driver continues to read and write UTF-8 while the server interprets the same bytes under a different encoding. The result is silent data corruption and a client/server charset-confusion mismatch. Charset confusion of this kind is also the primitive that can defeat byte-wise quoting/escaping when client and server disagree on a multi-byte encoding.
Impact
Silent data corruption and a client/server encoding mismatch once the connection's charset diverges from UTF-8. Because the mismatch undermines the assumption that quoting/escaping operates on UTF-8 bytes, it belongs to the charset-confusion class that can lead to SQL injection.
Patches
Fixed in 2.7.14, 3.3.5, 3.4.3, and 3.5.9. Upgrade to the patched release on your branch (3.5.x → 3.5.9, 3.4.x → 3.4.3, 3.0/3.1/3.2/3.3.x → 3.3.5, 2.x → 2.7.14). Once the connection is fully initialized, any subsequent charset change to a value that is not utf8 / utf8mb3 / utf8mb4 is rejected: the driver raises a SQLException with SQLState 08000 (connection exception) and closes the connection rather than continuing to exchange data under a mismatched encoding.
Workarounds
There is no reliable application-level workaround.
Credit
Reported by Yalguun Tumenkhuu (@fg0x0).