CVE-2026-55859

Received Received - Intake

MariaDB Connector/R2DBC Character Set Confusion

Publication date: 2026-08-28

Last updated on: 2026-08-28

Assigner: GitHub, Inc.

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-28

Last Modified

2026-08-28

Generated

2026-08-29

AI Q&A

2026-08-29

EPSS Evaluated

N/A

NVD

CVE-2026-55859

Affected Vendors & Products

Vendor	Product	Version / Range
org.mariadb	r2dbc-mariadb	to 1.4.1 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-838	The product uses or specifies an encoding when generating output to a downstream component, but the specified encoding is not the same as the encoding that is expected by the downstream component.
CWE-116	The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.

Attack-Flow Graph

Executive Summary

MariaDB Connector/R2DBC before 1.4.1 assumes all character data uses UTF-8 encoding. A server can change the character set mid-session via OK-packet or SET NAMES, causing the driver to send UTF-8 bytes while the server interprets them differently. This leads to silent data corruption and charset mismatches that can bypass security checks.

Detection Guidance

Detecting this vulnerability requires checking the version of MariaDB Connector/R2DBC in use. If your system uses version 1.4.1 or later, it is not vulnerable. For earlier versions, inspect applications using org.mariadb:r2dbc-mariadb for potential exposure to character set confusion attacks.

Impact Analysis

This flaw may corrupt data silently, leading to incorrect query execution, security bypasses, or application errors. It could allow unauthorized access or data leaks if quoting/escaping mechanisms are defeated due to charset confusion.

Compliance Impact

Silent data corruption and security bypasses could violate integrity requirements in GDPR and HIPAA. Unauthorized data access or leaks due to this flaw may lead to non-compliance with data protection regulations.

Mitigation Strategies

Upgrade to MariaDB Connector/R2DBC version 1.4.1 or later to address the vulnerability. If upgrading is not immediately possible, review and restrict server-side character set changes, especially those triggered by stored routines or triggers, to prevent charset-confusion mismatches.

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