---
id: "CVE-2026-101623"
kind: "vulnerability"
aliases: ["CVE-2026-101623"]
title: "MySQL Server: Optimizer flaw lets a privileged user crash the server"
severity: "medium"
cvss: 4.9
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["databases", "mysql", "package", "self-hosted"]
not_affected_if: ["no-high-privilege-accounts-exposed", "unaffected-version"]
published_at: "2026-10-20T22:18:16+00:00"
first_seen_at: "2026-10-23T21:57:22+00:00"
updated_at: "2026-10-25T04:31:33+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-101623", "first_seen_at": "2026-10-23T21:57:22+00:00"}]
---

# MySQL Server: Optimizer flaw lets a privileged user crash the server

A flaw in the MySQL Server optimizer lets a high-privileged attacker over the network trigger a hang or repeatable crash of MySQL Server and MySQL Cluster. The impact is denial of service only, with no confidentiality or integrity loss stated.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `SELECT VERSION();` on each MySQL Server and MySQL Cluster node and compare against the affected ranges: MySQL Server 8.4.0-8.4.12, 9.7.0-9.7.3, 26.7.0-26.7.1; MySQL Cluster 8.0.0-8.0.49, 8.4.0-8.4.12, 9.7.0-9.7.3, 26.7.0-26.7.1.

## Fix

- Upgrade MySQL Server and MySQL Cluster to a release outside the affected ranges, using the patched version named in Oracle's April 2026 Critical Patch Update advisory (version not stated in the sources).

## Timeline

- 2026-10-23T21:57:22+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-101623

## From the sources

Vulnerability in the MySQL Server, MySQL Cluster product of Oracle MySQL (component: Server: Optimizer).  Supported versions that are affected are MySQL Server: 8.4.0-8.4.12, 9.7.0-9.7.3, 26.7.0-26.7.1; MySQL Cluster: 8.0.0-8.0.49, 8.4.0-8.4.12, 9.7.0-9.7.3 and  26.7.0-26.7.1. Easily exploitable vulnerability allows high privileged attacker with network access via multiple protocols to compromise MySQL Server, MySQL Cluster.  Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server, MySQL Cluster. CVSS 3.1 Base Score 4.9 (Availability impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H).

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_