CVE-2026-55856 is a medium-severity (CVSS 5.9) CWE-522 vulnerability in org.mariadb.jdbc:mariadb-java-client. A fix is available for org.mariadb.jdbc:mariadb-java-client — see the affected versions and patch details below.
MariaDB Connector/J: Cleartext password disclosure to a MITM on the initial-handshake
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55856.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-55856 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 386,684 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
org.mariadb.jdbc:mariadb-java-client☕org.mariadb.jdbc:mariadb-java-client☕org.mariadb.jdbc:mariadb-java-client☕org.mariadb.jdbc:mariadb-java-clientReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Summary
When a Java application connects with sslMode=verify-full (or verify-ca) and a password but does not pin a server certificate, Connector/J deliberately accepts an untrusted/self-signed certificate at the TLS layer (the "MITM-proof without a CA" feature) and proves the server's identity afterwards by binding the certificate fingerprint into the authentication exchange. That fingerprint enforcement is applied to the OK-packet and auth-switch paths but not to the initial-handshake path. An active man-in-the-middle that presents a self-signed certificate, claims to be MariaDB, and names the initial authentication plugin mysql_clear_password receives the victim's database password in cleartext, before any fingerprint/identity check runs. The connection is torn down a moment later, but the credential is already gone.
Details
For sslMode=verify-full/verify-ca with a password and no serverSslCert/trustStore, the connector falls back to an ephemeral trust manager (default fallbackToSystemTrustStore=true) that accepts any non-expired certificate at the TLS layer and records its fingerprint. Identity is then meant to be enforced via that fingerprint.
The enforcement guard is present on two of the three paths, the OK-packet fingerprint check and the auth-switch handler (where the clear-password plugin is only allowed when the fingerprint is already verified). It is absent on the initial-handshake send: HandshakeResponse.encode() builds the mysql_clear_password response after checking only that SSL is enabled, never consulting the recorded fingerprint, sslMode, or whether the plugin is MITM-proof. By that point the connector already knows the certificate was self-signed. The clear-password plugin does not declare itself MITM-proof (it inherits the safe default), which confirms it is meant to be refused on an unverified certificate; the initial-handshake path simply never consults that flag. The initial path also bypasses restrictedAuth.
Impact
An active man-in-the-middle steals the full cleartext database password of any Java application using Connector/J with sslMode=verify-full/verify-ca plus a password and no pinned certificate, the configuration documented as the easy, secure default. With the captured credentials the attacker can take over the database account and read or modify all data that account is authorized for. The victim takes no unusual action; the developer explicitly enabled TLS verification expecting exactly this protection.
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). The fix applies the same certFingerprint != null && !isMitMProof() guard to the initial-handshake path before writing the auth response, refusing to send a mysql_clear_password (or any non-MITM-proof) response on an as-yet-unverified certificate, matching the auth-switch path.
Workarounds
If you cannot upgrade immediately, pin the server certificate (serverSslCert= the real CA / server cert). With a pinned certificate the self-signed certificate of a man-in-the-middle is rejected at the TLS layer before any password is transmitted.
Credit
Reported by haaahaaahiihiiii
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.mariadb.jdbc:mariadb-java-client | all versions | 2.7.14org.mariadb.jdbc:mariadb-java-client:2.7.14 |
| ☕Maven | org.mariadb.jdbc:mariadb-java-client | ≥ 3.0.0&&< 3.3.5 | 3.3.5org.mariadb.jdbc:mariadb-java-client:3.3.5 |
| ☕Maven | org.mariadb.jdbc:mariadb-java-client | ≥ 3.4.0&&< 3.4.3 | 3.4.3org.mariadb.jdbc:mariadb-java-client:3.4.3 |
| ☕Maven | org.mariadb.jdbc:mariadb-java-client | ≥ 3.5.0&&< 3.5.9 | 3.5.9org.mariadb.jdbc:mariadb-java-client:3.5.9 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.mariadb.jdbc:mariadb-java-client, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.mariadb.jdbc:mariadb-java-client to 2.7.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55856 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
MariaDB Connector/J (the JDBC driver used to connect Java applications to MariaDB and MySQL databases) does not consistently enforce certificate identity checks on the initial TLS handshake path. When an application connects with sslMode set to verify-full or verify-ca, supplies a password, and does not configure…
When using sslMode verify-ca or verify-full, configure serverSslCert or a trustStore so the JDBC client validates the server certificate before sending credentials. Upgrade to MariaDB Connector/J 2.7.14, 3.3.5, 3.4.3, or 3.5.9 when available in your product update stream.Source: Red Hat security advisory for CVE-2026-55856 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-55856 in your dependencies?
Find it across Maven, including transitive dependencies.