CVE-2026-55859 org.mariadb:r2dbc-mariadb has Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output
A character set mismatch in the MariaDB R2DBC connector allows silent data corruption and bypasses escaping mechanisms, potentially leading to security issues.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55859?
CVE-2026-55859 is a medium-severity vulnerability in mariadb-corporation mariadb-connector-r2dbc, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
MariaDB Connector/R2DBC is a non-blocking MariaDB and MySQL client implemented in Java. Prior to 1.4.1, org.mariadb:r2dbc-mariadb encodes and decodes all character data under the assumption that the connection character set is UTF-8. A server can announce a mid-session change to character_set_client through the OK-packet session-state-tracking mechanism, including through SET NAMES executed by a stored routine or trigger, server configuration, or a hostile or man-in-the-middle server. If the new character set is not UTF-8, the driver continues to exchange UTF-8 while the server interprets the same bytes under a different encoding, causing silent data corruption and a client/server charset-confusion mismatch that can defeat byte-wise quoting or escaping. The fix accepts only utf8, utf8mb3, or utf8mb4 after initialization; any other value raises R2dbcNonTransientResourceException with SQLState 08000 and closes the connection. This issue is fixed in version 1.4.1.
Which versions are affected by CVE-2026-55859?
2 open source packages ship an affected version, including org.mariadb:r2dbc-mariadb.
| Package | Affected | Fixed in |
|---|---|---|
org.mariadb:r2dbc-mariadb Maven | All versions | 1.4.1 |
org.mariadb:r2dbc-mariadb Maven | All versions | 1.4.1 |
How do I fix CVE-2026-55859?
Upgrade org.mariadb:r2dbc-mariadb to 1.4.1 or later.
Is CVE-2026-55859 being exploited?
There is no known exploitation of CVE-2026-55859 in the wild and no public exploit code.
Sources
Also known as GHSA-5rqc-86vf-g8r2.