CVE-2026-55858 is a medium-severity (CVSS 5.9) CWE-838 vulnerability in org.mariadb.jdbc:mariadb-java-client. O3 Security confirms whether CVE-2026-55858 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
org.mariadb.jdbc:mariadb-java-client has Inappropriate Encoding for Output Context
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
The connector encodes and decodes all character data assuming the connection character set is UTF-8. A server can change character_set_client 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).
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-2026-55858 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-2026-55858 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-2026-55858. 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-2026-55858 in your dependencies?
O3 detects CVE-2026-55858 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.