CVE-2026-55859: R2dbc mariadb R2dbc-mariadb Has Inappropriate Encoding For Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5rqc-86vf-g8r2",
  "modified" : "2026-08-28T22:49:03Z",
  "published" : "2026-08-28T22:49:03Z",
  "aliases" : [ "CVE-2026-55859" ],
  "summary" : "org.mariadb:r2dbc-mariadb has Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output",
  "details" : "### 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/)).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.mariadb:r2dbc-mariadb"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.4.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/mariadb-corporation/mariadb-connector-r2dbc/security/advisories/GHSA-5rqc-86vf-g8r2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mariadb-corporation/mariadb-connector-r2dbc/commit/38bad9afebc6c581a853656a42f9ebf403b1b1b7"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mariadb-corporation/mariadb-connector-r2dbc"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mariadb-corporation/mariadb-connector-r2dbc/releases/tag/1.4.1"
  }, {
    "type" : "WEB",
    "url" : "https://jira.mariadb.org/browse/R2DBC-124"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-116", "CWE-838" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-28T22:49:03Z",
    "nvd_published_at" : null
  }
}