CVE-2021-2016Network attack vector

Privileged remote denial of service via optimizer crash

Published Jan 20, 2021 · Updated Sep 26, 2024

MySQL Server 8.0.19 and earlier contain a denial-of-service flaw in the Server Optimizer that remote authenticated users can trigger through the MySQL protocol. The optimizer mishandles crafted query input, causing the server process to hang or repeatedly crash. Exploitation requires high privileges and network access; impact is limited to interrupting MySQL availability, with no confidentiality or integrity loss reported.

CVSS severity4.9
Medium
EPSS probability2.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

MySQL Server 8.0.19 and earlier contain a denial-of-service flaw in the Server Optimizer that remote authenticated users can trigger through the MySQL protocol. The optimizer mishandles crafted query input, causing the server process to hang or repeatedly crash. Exploitation requires high privileges and network access; impact is limited to interrupting MySQL availability, with no confidentiality or integrity loss reported.

The record

CVE
CVE-2021-2016
Published
Jan 20, 2021
Updated
Sep 26, 2024
Vendor
Oracle Corporation
Product
MySQL Server
Classifications
T1499
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jan 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 26, 2024Record 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=8.0.19 and prior

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Oracle Corporation · MySQL Serverversion=8.0.19 and prior

Published CVSS scores

6.8National Vulnerability DatabaseAV:N/AC:L/Au:S/C:N/I:N/A:C
4.9Oracle CorporationCVSS: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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

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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