{"id":"CVE-2026-55859","aliases":["EUVD-2026-68022","GHSA-5rqc-86vf-g8r2"],"status":"published","title":"MariaDB Connector/R2DBC: Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output in org.mariadb:r2dbc-mariadb","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.","severity":{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00486,"percentile":0.42183,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-116","CWE-838"],"published":"2026-08-28T22:48:41Z","modified":"2026-10-28T11:17:50Z","fixes":[{"ecosystem":"Maven","package":"org.mariadb:r2dbc-mariadb","fixed_in":["1.4.1"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Maven","package":"org.mariadb:r2dbc-mariadb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.4.1"}]}]},{"source":"osv","ecosystem":"Maven","package":"org.mariadb:r2dbc-mariadb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.4.1"}]}],"versions":["0.8.1-alpha1","0.8.2-alpha2","0.8.3-beta1","0.8.4-rc","1.0.0","1.0.1","1.0.2","1.0.3","1.1.0-beta","1.1.1-rc","1.1.2","1.1.3","1.1.4","1.2.0","1.2.1","1.2.2","1.2.3","1.3.0","1.3.1","1.4.0"]}],"products":[{"vendor":"mariadb-corporation","product":"mariadb-connector-r2dbc"},{"vendor":"org.mariadb","product":"r2dbc-mariadb"}],"references":[{"url":"https://github.com/mariadb-corporation/mariadb-connector-r2dbc/security/advisories/GHSA-5rqc-86vf-g8r2","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://github.com/mariadb-corporation/mariadb-connector-r2dbc/commit/38bad9afebc6c581a853656a42f9ebf403b1b1b7","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/mariadb-corporation/mariadb-connector-r2dbc/releases/tag/1.4.1","tags":["x_refsource_MISC","web"]},{"url":"https://jira.mariadb.org/browse/R2DBC-124","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/advisories/GHSA-5rqc-86vf-g8r2"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55859.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55859","tags":["advisory"]},{"url":"https://github.com/mariadb-corporation/mariadb-connector-r2dbc","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-55859","title":"MariaDB Connector/R2DBC: Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output in org.mariadb:r2dbc-mariadb","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.","status":"published","published":"2026-08-28T22:48:41.592Z","modified":"2026-08-31T18:53:25.642Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-116","CWE-838"],"updated_at":"2026-11-02T14:20:11.925815Z"}],"euvd":[{"id":"EUVD-2026-68022","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.","status":"published","published":"2026-08-28T22:48:41Z","modified":"2026-08-31T18:53:25Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"updated_at":"2026-11-02T18:01:19.818565Z"}],"ghsa":[{"id":"GHSA-5rqc-86vf-g8r2","title":"org.mariadb:r2dbc-mariadb has Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output","description":"### Summary\n\nThe connector encodes and decodes all character data assuming the connection character set is UTF-8. A server can change character_set_client mid-session to a non-UTF-8 charset, after which the driver and server interpret the same bytes under different encodings, causing silent data corruption and a client/server charset-confusion mismatch.\n\n### Details\n\nThe driver encodes and decodes all character data on the assumption that the connection character set is UTF-8. The server can, however, announce a change of character_set_client mid-session through the OK-packet session-state-tracking mechanism, for example via a SET NAMES … run by a stored routine or trigger, by server configuration, or by a hostile server.\n\nIf the new charset is not UTF-8, the driver continues to read and write UTF-8 while the server interprets the same bytes under a different encoding. The result is silent data corruption and a client/server charset-confusion mismatch. Charset confusion of this kind is also the primitive that can defeat byte-wise quoting/escaping when client and server disagree on a multi-byte encoding.\n\n### Am I affected?\n\nYou are affected if you use mariadb Connector/R2DBC (org.mariadb:r2dbc-mariadb) below 1.4.1 and a connection can be steered, by a hostile or man-in-the-middle server, or by server-side state such as a stored routine, trigger, or configuration — to switch character_set_client to a non-UTF-8 value mid-session.\n\n### Impact\n\nSilent data corruption and a client/server encoding mismatch once the connection's charset diverges from UTF-8. Because the mismatch undermines the assumption that quoting/escaping operates on UTF-8 bytes, it belongs to the charset-confusion class that can lead to SQL injection.\n\n### Patches\n\nFixed in 1.4.1. Once the connection is fully initialized, any subsequent charset change to a value that is not utf8 / utf8mb3 / utf8mb4 is rejected: the driver raises R2dbcNonTransientResourceException (SQLState 08000) and closes the connection rather than continuing to exchange data under a mismatched encoding. Upgrade to 1.4.1 or later.\n\n### Workarounds\n\nThere is no reliable application-level workaround; upgrade to 1.4.1 or later.\n\n### Credit\n\nReported by Yalguun Tumenkhuu ([@fg0x0](https://github.com/fg0x0/)).","status":"published","published":"2026-08-28T22:49:03Z","modified":"2026-08-28T22:49:04Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-116","CWE-838"],"updated_at":"2026-11-02T14:41:08.084849Z"}],"nvd":[{"id":"CVE-2026-55859","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.","status":"published","published":"2026-08-28T23:17:09.007Z","modified":"2026-09-08T21:08:37.32Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-116","CWE-838"],"updated_at":"2026-11-02T14:12:42.366888Z"}],"osv":[{"id":"CVE-2026-55859","title":"MariaDB Connector/R2DBC: Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output in org.mariadb:r2dbc-mariadb","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.","status":"published","published":"2026-08-28T22:48:41.592Z","modified":"2026-10-28T11:17:50.020995859Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-116","CWE-838"],"updated_at":"2026-11-02T15:45:11.609219Z"},{"id":"GHSA-5rqc-86vf-g8r2","title":"org.mariadb:r2dbc-mariadb has Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output","description":"### Summary\n\nThe connector encodes and decodes all character data assuming the connection character set is UTF-8. A server can change character_set_client mid-session to a non-UTF-8 charset, after which the driver and server interpret the same bytes under different encodings, causing silent data corruption and a client/server charset-confusion mismatch.\n\n### Details\n\nThe driver encodes and decodes all character data on the assumption that the connection character set is UTF-8. The server can, however, announce a change of character_set_client mid-session through the OK-packet session-state-tracking mechanism, for example via a SET NAMES … run by a stored routine or trigger, by server configuration, or by a hostile server.\n\nIf the new charset is not UTF-8, the driver continues to read and write UTF-8 while the server interprets the same bytes under a different encoding. The result is silent data corruption and a client/server charset-confusion mismatch. Charset confusion of this kind is also the primitive that can defeat byte-wise quoting/escaping when client and server disagree on a multi-byte encoding.\n\n### Am I affected?\n\nYou are affected if you use mariadb Connector/R2DBC (org.mariadb:r2dbc-mariadb) below 1.4.1 and a connection can be steered, by a hostile or man-in-the-middle server, or by server-side state such as a stored routine, trigger, or configuration — to switch character_set_client to a non-UTF-8 value mid-session.\n\n### Impact\n\nSilent data corruption and a client/server encoding mismatch once the connection's charset diverges from UTF-8. Because the mismatch undermines the assumption that quoting/escaping operates on UTF-8 bytes, it belongs to the charset-confusion class that can lead to SQL injection.\n\n### Patches\n\nFixed in 1.4.1. Once the connection is fully initialized, any subsequent charset change to a value that is not utf8 / utf8mb3 / utf8mb4 is rejected: the driver raises R2dbcNonTransientResourceException (SQLState 08000) and closes the connection rather than continuing to exchange data under a mismatched encoding. Upgrade to 1.4.1 or later.\n\n### Workarounds\n\nThere is no reliable application-level workaround; upgrade to 1.4.1 or later.\n\n### Credit\n\nReported by Yalguun Tumenkhuu ([@fg0x0](https://github.com/fg0x0/)).","status":"published","published":"2026-08-28T22:49:03Z","modified":"2026-08-28T23:10:37.561415Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-116","CWE-838"],"updated_at":"2026-11-02T15:46:38.911014Z"}]}}