CVE-2026-55859

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 77% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.9Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
5.9
EG Score
5.9(medium)
EG Risk
27(Track)
EG Risk 27/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity59% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
23%
KEV
Not listed

Published

August 28, 2026

Last Modified

September 8, 2026

Advisory Details (4)

Auto-updated Aug 28, 2026
Patch available. Sources: github, github_commit, github_release.
generic

[R2DBC-124] Ensure a non-UTF8 charset cannot be used for protocol exchanges - Jira

https://jira.mariadb.org/browse/R2DBC-124
github_release Patch Available

MariaDB Connector/R2DBC 1.4.1

Patch available: mariadb-corporation/mariadb-connector-r2dbc 1.4.1

https://github.com/mariadb-corporation/mariadb-connector-r2dbc/releases/tag/1.4.1
github_commit Patch Available

commit 38bad9afebc6 (mariadb-corporation/mariadb-connector-r2dbc)

Patch available: mariadb-corporation/mariadb-connector-r2dbc 1.4.1 (contains commit 38bad9afebc6)

https://github.com/mariadb-corporation/mariadb-connector-r2dbc/commit/38bad9afebc6c581a853656a42f9ebf403b1b1b7
github Patch Available

Inappropriate Encoding for Output Context and Improper Encoding or Escaping of Output in org.mariadb:r2dbc-mariadb · Advisory · mariadb-corporation/mariadb-connector-r2dbc · GitHub

Affected: 1.4.1. Once the connection is fully initialized, any subsequent charset change to

https://github.com/mariadb-corporation/mariadb-connector-r2dbc/security/advisories/GHSA-5rqc-86vf-g8r2

Vendor Advisories for CVE-2026-55859(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.mariadb:r2dbc-mariadb0.8.1-alpha1 ... 1.4.0 (20 versions)1.4.1—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 38× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-18 22:01 UTCEG score recompute
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-17 22:19 UTCEG score recompute
  4. 2026-09-17 19:31 UTCEPSS rescore
  5. 2026-09-16 22:37 UTCEG score recompute
  6. 2026-09-16 14:08 UTCEPSS rescore
  7. 2026-09-16 05:15 UTCEPSS rescore
  8. 2026-09-15 22:28 UTCEG score recompute
  9. 2026-09-15 03:11 UTCEPSS rescore
  10. 2026-09-13 23:04 UTCEG score recompute
  11. 2026-09-13 16:47 UTCEPSS rescore
  12. 2026-09-12 23:22 UTCEG score recompute
  13. 2026-09-11 23:40 UTCEG score recompute
  14. 2026-09-11 14:53 UTCEPSS rescore
  15. 2026-09-10 23:57 UTCEG score recompute
  16. 2026-09-10 09:35 UTCEPSS rescore
  17. 2026-09-09 23:52 UTCEG score recompute
  18. 2026-09-08 22:01 UTCEPSS rescore
  19. 2026-09-07 18:53 UTCEG score recompute
  20. 2026-09-07 16:01 UTCEPSS rescore
  21. 2026-09-06 19:12 UTCEG score recompute
  22. 2026-09-06 13:47 UTCEPSS rescore
  23. 2026-09-05 19:30 UTCEG score recompute
  24. 2026-09-04 19:48 UTCEG score recompute
  25. 2026-09-04 05:07 UTCEPSS rescore
Show 13 more
  1. 2026-09-02 20:23 UTCEG score recompute
  2. 2026-09-02 14:12 UTCEPSS rescore
  3. 2026-09-01 19:17 UTCEG score recompute
  4. 2026-09-01 13:54 UTCEPSS rescore
  5. 2026-09-01 04:40 UTCEPSS rescore
  6. 2026-08-31 19:29 UTCEG score recompute
  7. 2026-08-31 18:56 UTCEG score recompute
  8. 2026-08-30 22:47 UTCEG score recompute
  9. 2026-08-30 19:17 UTCEPSS rescore
  10. 2026-08-30 01:22 UTCEPSS rescore
  11. 2026-08-28 23:24 UTCEG score recompute
  12. 2026-08-28 23:01 UTCEG score recompute
  13. 2026-08-28 22:58 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-55859?
CVE-2026-55859 is a medium vulnerability published on August 28, 2026. 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 charactersetclient…
When was CVE-2026-55859 disclosed?
CVE-2026-55859 was first published in the National Vulnerability Database on August 28, 2026, with the most recent update on September 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55859 actively exploited?
CVE-2026-55859 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 77.4% of all scored CVEs.
What is the CVSS score of CVE-2026-55859?
CVE-2026-55859 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2026-55859?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55859, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-55859

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