CVE-2026-55858 is a medium-severity (CVSS 5.9) CWE-838 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: Inappropriate Encoding for Output Context in org.mariadb.jdbc:mariadb-java-client
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-2026-55858.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-55858 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 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
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 | 2.7.14org.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-2026-55858 is resolved across your whole dependency graph.
Workarounds
Until you can upgrade, make sure every query built from user input uses parameterised statements or a prepared-statement API rather than string concatenation, and reduce the database account's privileges so an injected query cannot read or alter data beyond what the feature needs.
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 (org.mariadb.jdbc:mariadb-java-client) encodes and decodes the wire protocol and performs client-side escaping assuming a UTF-8 connection character set. If the server signals a mid-session change of character_set_client to a non-UTF-8 value (via SET NAMES, a stored routine or trigger, server…
Upgrade MariaDB Connector/J to a fixed version (2.7.14, 3.3.5, 3.4.3, or 3.5.9, as appropriate for the branch in use), which rejects any post-initialization character set other than utf8, utf8mb3, or utf8mb4 and closes the connection. Where upgrading is not immediately possible, avoid changing character_set_client after connection establishment and connect only to trusted database servers.Source: Red Hat security advisory for CVE-2026-55858 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-55858 in your dependencies?
Find it across Maven, including transitive dependencies.