Summary
org.mariadb.jdbc:mariadb-java-client has Inappropriate Encoding for Output Context
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.
Workarounds
There is no reliable application-level workaround.
Credit
Reported by Yalguun Tumenkhuu (@fg0x0).
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.
CVE-2026-55858 has a CVSS score of 5.9 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.7.14, 3.3.5, 3.4.3, 3.5.9); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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.
Frequently Asked Questions
- What is CVE-2026-55858? CVE-2026-55858 is a medium-severity security vulnerability in org.mariadb.jdbc:mariadb-java-client (maven), affecting versions < 2.7.14. It is fixed in 2.7.14, 3.3.5, 3.4.3, 3.5.9.
- How severe is CVE-2026-55858? CVE-2026-55858 has a CVSS score of 5.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.mariadb.jdbc:mariadb-java-client are affected by CVE-2026-55858? org.mariadb.jdbc:mariadb-java-client (maven) versions < 2.7.14 is affected.
- Is there a fix for CVE-2026-55858? Yes. CVE-2026-55858 is fixed in 2.7.14, 3.3.5, 3.4.3, 3.5.9. Upgrade to this version or later.
- Is CVE-2026-55858 exploitable, and should I be worried? Whether CVE-2026-55858 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-55858 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-55858?
- Upgrade
org.mariadb.jdbc:mariadb-java-clientto 2.7.14 or later - Upgrade
org.mariadb.jdbc:mariadb-java-clientto 3.3.5 or later - Upgrade
org.mariadb.jdbc:mariadb-java-clientto 3.4.3 or later - Upgrade
org.mariadb.jdbc:mariadb-java-clientto 3.5.9 or later
- Upgrade