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CVE-2026-55859— MariaDB Connector/R2DBC: Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output in org.mariadb:r2dbc-mariadb

Quick assessment

Affected
mariadb-corporation mariadb-connector-r2dbc
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

MariaDB Connector/R2DBC 是一个以 Java 实现的非阻塞 MariaDB 和 MySQL 客户端。在 1.4.1 之前， 在编解码所有字符数据时，均默认假设连接的字符集为 UTF-8。服务器可以通过 OK 报文中的会话状态跟踪机制，在会话中途宣布 发生变更，这种变更可能由存储过程、触发器执行的 、服务器配置，或来自敌意服务器或中间人攻击服务器引起。如果新的字符集不是 UTF-8，驱动程序仍继续以 UTF-8 进行数据交换，而服务器则按不同的编码解释这些字节，从而导致静默的数据损坏，并造成客户

CVSS 5.9 · Medium

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle
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I. Basic Information for CVE-2026-55859

Vulnerability Information
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Vulnerability Title
MariaDB Connector/R2DBC: Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output in org.mariadb:r2dbc-mariadb
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对输出编码和转义不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
mariadb-corporation mariadb-connector-r2dbc < 1.4.1 -
org.mariadb r2dbc-mariadb < 1.4.1 -

II. Public POCs for CVE-2026-55859

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III. Intelligence Information for CVE-2026-55859

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Patches & Fixes for CVE-2026-55859 (1)

Vendor Advisories for CVE-2026-55859 (1)

Vendor Pages for CVE-2026-55859 (1)

Other References for CVE-2026-55859 (1)

Same Patch Batch · mariadb-corporation · 2026-08-28 · 8 CVEs total

CVE-2026-55215 7.5 HIGH MariaDB Connector/Node.js: Connector leaks the cleartext password to an MitM despite `ssl:
CVE-2026-55855 6.5 MEDIUM MariaDB Connector/Node.js: Possible SQL injection in Buffer parameter escaping under big5/
CVE-2026-55854 5.9 MEDIUM MariaDB Connector/Node.js: Cleartext Transmission of Sensitive Information and Insufficien
CVE-2026-55856 5.9 MEDIUM MariaDB Connector/J: Cleartext password disclosure to a MITM on the initial-handshake
CVE-2026-55860 5.9 MEDIUM MariaDB Connector/R2DBC: Cleartext password disclosure to a man-in-the-middle server (clea
CVE-2026-55857 5.9 MEDIUM MariaDB Connector/J: Cleartext Transmission of Sensitive Information and Insufficiently Pr
CVE-2026-55858 5.9 MEDIUM MariaDB Connector/J: Inappropriate Encoding for Output Context in org.mariadb.jdbc:mariadb

IV. Related Vulnerabilities

Same product: mariadb-connector-r2dbc
Same vendor: mariadb-corporation
Same weakness: CWE-116

V. Comments for CVE-2026-55859

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