CVE-2026-55856 MariaDB Connector/J: Cleartext password disclosure to a MITM on the initial-handshake
An active man-in-the-middle can steal database passwords during the initial handshake if specific SSL verification settings are used without explicit trust store configuration.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55856?
CVE-2026-55856 is a medium-severity vulnerability in mariadb-corporation mariadb-connector-j, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
MariaDB Connector/J is used to connect applications developed in Java to MariaDB and MySQL databases. Prior to 2.7.14, 3.3.5, 3.4.3, and 3.5.9, when a Java application connects with sslMode=verify-full or sslMode=verify-ca, supplies a password, and does not configure serverSslCert or trustStore, Connector/J can accept an untrusted self-signed certificate through the fallbackToSystemTrustStore=true ephemeral trust manager and record its certFingerprint for later identity binding. The OK-packet and authentication-switch paths enforce the certificate fingerprint, but the initial-handshake path does not. HandshakeResponse.encode() can therefore build and send a mysql_clear_password response before checking certFingerprint != null && !isMitMProof(), sslMode, or whether the authentication plugin is resistant to a man-in-the-middle, and the initial path also bypasses restrictedAuth. An active man-in-the-middle or hostile server can present a self-signed certificate, claim to be MariaDB, select mysql_clear_password as the initial authentication plugin, and receive the full database password before the connection is rejected. This issue is fixed in versions 2.7.14, 3.3.5, 3.4.3, and 3.5.9.
Weakness: CWE-522
Which versions are affected by CVE-2026-55856?
8 open source packages ship an affected version, including org.mariadb.jdbc:mariadb-java-client.
| Package | Affected | Fixed in |
|---|---|---|
org.mariadb.jdbc:mariadb-java-client Maven | All versions | 2.7.14 |
org.mariadb.jdbc:mariadb-java-client Maven | All versions | 2.7.14 |
org.mariadb.jdbc:mariadb-java-client Maven | From 3.0.0 | 3.3.5 |
org.mariadb.jdbc:mariadb-java-client Maven | From 3.0.0 | 3.3.5 |
org.mariadb.jdbc:mariadb-java-client Maven | From 3.4.0 | 3.4.3 |
org.mariadb.jdbc:mariadb-java-client Maven | From 3.4.0 | 3.4.3 |
2 more packages
org.mariadb.jdbc:mariadb-java-client Maven | From 3.5.0 | 3.5.9 |
org.mariadb.jdbc:mariadb-java-client Maven | From 3.5.0 | 3.5.9 |
How do I fix CVE-2026-55856?
Upgrade org.mariadb.jdbc:mariadb-java-client to a fixed version for your release line: 2.7.14, 3.3.5, 3.4.3 or 3.5.9.
Is CVE-2026-55856 being exploited?
There is no known exploitation of CVE-2026-55856 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-EO42175, CLEANSTART-2026-MO09576, CLEANSTART-2026-WK92000, CLEANSTART-2026-YJ93143, ECHO-b9d6-8b57-95e5, GHSA-g9jj-cgmh-9f38 and 15 more.