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MySQL Server EUVDEUVD-2026-106199

| CVE-2026-101798 MEDIUM
Improper Access Control (CWE-284)
2026-10-20 secalert_us@oracle.com GHSA-rhc8-f9x8-5w7r
4.9
CVSS 3.1 · Vendor: oracle
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Authenticate with high-privilege MySQL account
  2. Delivery
    Connect over network protocol
  3. Exploit
    Submit crafted query to Optimizer
  4. Execution
    Trigger hang or repeatable crash
  5. Impact
    Complete denial of service

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Access control enforcement
MITRE ATT&CK

1 technique across 1 tactic: Defense Evasion

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires an attacker to already possess high-privilege credentials on the target (PR:H) and network reach to the MySQL Server/Cluster via one of the supported protocols; the flaw is triggered through the Server: Optimizer component. Affected builds are MySQL Server 8.4.0-8.4.12, 9.7.0-9.7.3, 26.7.0-26.7.1 and 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. The decisive limiting factor is the high-privilege prerequisite: an unprivileged or external attacker cannot reach this condition, so realistic abuse comes from a malicious or compromised privileged account rather than anonymous attackers. Impact is limited to denial of service (no data disclosure or modification).

Impact

This is a moderate-severity availability-only flaw, consistent with its CVSS 3.1 base score of 4.9. The vector (AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H) shows network reach and low attack complexity, but critically requires PR:H - high privileges on the MySQL Server/Cluster - which sharply limits the attacker population to users who already hold elevated database credentials. Impact is confined to availability (C:N/I:N/A:H): a hang or repeatable crash producing a complete denial of service, with no confidentiality or integrity consequence. No EPSS score, KEV listing, SSVC decision, or POC was provided in the input, so there is no signal of active or probable exploitation; status is no public exploit identified at time of analysis. The signals are internally consistent - Oracle's own 'easily exploitable' phrasing aligns with AC:L, while the 'high privileged' phrasing aligns with PR:H - so this reads as a genuine but lower-priority issue: real and patchable, but gated behind privileged access and limited to DoS rather than a widely weaponizable critical bug. The main caveat is that EPSS and POC data are simply absent (not confirmed negative), so exploitation likelihood could not be quantified.

Exploit ScenarioDerived

An attacker who already holds high-privilege MySQL credentials (or has compromised such an account) connects over the network via one of the supported protocols and submits a crafted query that the Server: Optimizer component mishandles, causing the server to hang or repeatedly crash. The result is a complete denial of service for the MySQL Server or Cluster. No public proof-of-concept exploit was identified in the provided data.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 21, 2026

Denial of service in Oracle MySQL Server and MySQL Cluster lets an attacker who already holds high-privilege database credentials hang or repeatedly crash the server through the Server: Optimizer component, reachable over the network via multiple protocols. Affected builds are MySQL Server 8.4.0-8.4.12, 9.7.0-9.7.3 and 26.7.0-26.7.1, plus 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. The CVSS 3.1 base score is 4.9 (AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H), reflecting availability-only impact with no disclosure or modification of data; no public exploit code or confirmed active exploitation was identified at time of analysis, and the PR:H prerequisite means realistic abuse comes from a malicious or compromised privileged account rather than anonymous external attackers.

RemediationAI

Apply the October 2026 Oracle Critical Patch Update (https://www.oracle.com/security-alerts/cpuoct2026.html), which is the vendor-released fix for this issue; the supplied data does not enumerate the exact patched version numbers, so confirm the CPU October 2026 minimum version for each product line on the Oracle advisory before upgrading MySQL Server 8.4.x, 9.7.x or 26.7.x and MySQL Cluster 8.0.x, 8.4.x, 9.7.x or 26.7.x. Because exploitation requires high-privilege credentials, the most effective interim control is privilege reduction: audit and revoke unnecessary high-privilege grants (SYSTEM_USER, broad ALL PRIVILEGES grants, and non-essential administrative accounts) and move routine workloads onto minimally privileged accounts, at the cost of administrative convenience and possible application breakage if schemas depend on escalated grants. Restrict network reachability to the MySQL Server and Cluster ports to trusted application subnets and management hosts via firewall or bind-address/listener rules, accepting reduced operational flexibility. As a covering measure against hang-style abuse, set per-session statement limits such as max_execution_time and resource-group CPU limits so a runaway optimizer plan is terminated rather than pinning the instance; these limits will also abort legitimately long-running analytical queries. Do not rely on POC status as a deferral signal: no public exploit code was identified at time of analysis, but the flaw is remotely reachable and low in attack complexity once credentials are held.

Affected VersionsENISA

MySQL Cluster 8.4.0-8.4.12
MySQL Server 9.7.0-9.7.3
MySQL Cluster 8.0.0-8.0.49
MySQL Cluster 9.7.0-9.7.3
MySQL Cluster 26.7.0-26.7.1
MySQL Server 8.4.0-8.4.12
MySQL Server 26.7.0-26.7.1

Affected Packages

euvd mysql_cluster no fix
euvd mysql_server no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The flaw sits in the Server: Optimizer component of Oracle MySQL, the query-planning subsystem that parses and rewrites SQL, evaluates access paths and chooses execution strategies (index vs. table scans, join orders, subquery materialization) before handing a plan to the storage engine. Because the trigger is exercised through optimizer code paths reachable over the network via multiple protocols, a crafted statement from a sufficiently privileged session can drive the optimizer into a state that hangs the server instance or crashes it repeatedly, yielding a complete denial of service against the affected instance or cluster. No CWE identifier was assigned in the supplied data, but the observable behavior is a resource/lifecycle handling defect in query planning rather than memory corruption with a disclosed write primitive; the CVSS vector confirms scope-unchanged, availability-only (C:N/I:N/A:H) impact, and the AC:L/PR:H/UI:N components indicate the condition is reliably reachable once high privileges are present, with no user interaction. MySQL Cluster is affected across a broader version span (including the 8.0.x line) than MySQL Server, indicating the same optimizer code is shared into the cluster distribution.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (oracle) PRIMARY 4.9 MEDIUM
AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
vuln.today AI 4.9 MEDIUM

Network-reachable (AV:N) and easily exploitable (AC:L) per Oracle, but requires high-privilege database access (PR:H); impact is availability-only DoS (A:H, C:N/I:N).

3.1 AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Red Hat 4.9 MEDIUM

Primary rating from Vendor (oracle).

CVSS VectorVendor: oracle

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

DescriptionCVE.org

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).

Threat Intelligence Overview

EPSS Score
0.4%
Top 65% exploitable
Prevalence
Ubiquitous
MySQL is among the most widely deployed databases worldwide
Data Quality
4 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.4%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

24
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +24
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Vendor StatusVendor

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