# CVE-2026-55859

## Summary

- **CVE ID:** CVE-2026-55859
- **Severity:** MEDIUM
- **CVSS Score:** 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N)
- **CWE:** CWE-116, CWE-838
- **Published:** Aug 28, 2026
- **Last Modified:** Aug 31, 2026

## 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.

## Affected Products

- mariadb-corporation — mariadb-connector-r2dbc (< 1.4.1)
- org.mariadb — r2dbc-mariadb (< 1.4.1)

## References

- [CNA](https://github.com/mariadb-corporation/mariadb-connector-r2dbc/security/advisories/GHSA-5rqc-86vf-g8r2)
- [CNA](https://github.com/mariadb-corporation/mariadb-connector-r2dbc/commit/38bad9afebc6c581a853656a42f9ebf403b1b1b7)
- [CNA](https://github.com/mariadb-corporation/mariadb-connector-r2dbc/releases/tag/1.4.1)
- [CNA](https://jira.mariadb.org/browse/R2DBC-124)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.30%
- **EPSS Percentile:** 22.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._