CVE-2026-21948Network attack vector

Server hang or crash via undisclosed optimizer flaw

Published Jan 20, 2026 · Updated Jan 20, 2026

Denial of service in Oracle MySQL Server allows remote authenticated users to hang or repeatedly crash affected servers. Oracle identifies the Server Optimizer as the affected component but has not published the operation or input condition that exhausts resources. Exploitation requires high privileges and network access; versions 8.0.0 through 8.0.44, 8.4.0 through 8.4.7, and 9.0.0 through 9.5.0 are affected.

CVSS severity4.9
Medium
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Oracle MySQL Server allows remote authenticated users to hang or repeatedly crash affected servers. Oracle identifies the Server Optimizer as the affected component but has not published the operation or input condition that exhausts resources. Exploitation requires high privileges and network access; versions 8.0.0 through 8.0.44, 8.4.0 through 8.4.7, and 9.0.0 through 9.5.0 are affected.

The record

CVE
CVE-2026-21948
Published
Jan 20, 2026
Updated
Jan 20, 2026
Vendor
Oracle
Product
MySQL Server
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jan 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=8.0.0 <=8.0.44
  2. Affected versionversion=8.4.0 <=8.4.7
  3. Affected versionversion=9.0.0 <=9.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Oracle · MySQL Serverversion=8.0.0 <=8.0.44; version=8.4.0 <=8.4.7; version=9.0.0 <=9.5.0

Published CVSS scores

4.9OracleCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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