CVE-2026-55859: MariaDB Connector/R2DBC: Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output in org.mariadb:r2dbc-mariadb
Vulnerability summary
CVE-2026-55859 is a medium (CVSS 5.9) Improper Encoding or Escaping of Output vulnerability in mariadb-corporation mariadb-connector-r2dbc. EPSS estimates a 0.49% chance of exploitation in the next 30 days, higher than 41.9% of scored vulnerabilities.
Not severe (CVSS 5.9, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Timeline
- 28-08-2026PublishedVulnerability first disclosed.
- 31-08-2026Last modifiedVulnerability information updated.
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 metrics
3 scores · 3 sources · 1 version- OSV · MavenEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
- NVDNIST5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS trend
Probability
0.49%
Chance of exploitation in the next 30 days
Percentile
42%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.49% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-116Improper Encoding or Escaping of OutputThe 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.
- CWE-838Inappropriate Encoding for Output ContextThe 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.
Affected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Org.mariadb2 products
- r2dbc-mariadb< 1.4.1
- r2dbc-mariadb< 1.4.1
Mariadb-corporation1 product
- mariadb-connector-r2dbc< 1.4.1
2 vendors · 3 products