CVE-2026-55856 is a medium-severity (CVSS 5.9) CWE-522 vulnerability in org.mariadb.jdbc:mariadb-java-client. O3 Security confirms whether CVE-2026-55856 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
MariaDB has cleartext password disclosure to a MITM on the initial-handshake
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 | 2.7.14 |
| ☕Maven | org.mariadb.jdbc:mariadb-java-client | ≥ 3.0.0&&< 3.3.5 | 3.3.5 |
| ☕Maven | org.mariadb.jdbc:mariadb-java-client | ≥ 3.4.0&&< 3.4.3 | 3.4.3 |
| ☕Maven | org.mariadb.jdbc:mariadb-java-client | ≥ 3.5.0&&< 3.5.9 | 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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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.
How O3 protects you
O3 pinpoints whether CVE-2026-55856 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-55856. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-55856 in your dependencies?
O3 detects CVE-2026-55856 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.