CVE-2021-2390Network attack vector

Unauthenticated denial of service via memcached integer underflow

Published Jul 20, 2021 · Updated Sep 26, 2024

Integer underflow in Oracle MySQL Server 5.7.34 and earlier and 8.0.25 and earlier allows remote attackers to hang or crash the server. The memcached plugin processes authentication commands without properly validating user-supplied data, allowing an integer to underflow before a memory write. Oracle rates exploitation as high-complexity and availability-only, while ZDI reports unauthenticated code execution in the service account context.

CVSS severity5.9
Medium
EPSS probability4.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer underflow in Oracle MySQL Server 5.7.34 and earlier and 8.0.25 and earlier allows remote attackers to hang or crash the server. The memcached plugin processes authentication commands without properly validating user-supplied data, allowing an integer to underflow before a memory write. Oracle rates exploitation as high-complexity and availability-only, while ZDI reports unauthenticated code execution in the service account context.

The record

CVE
CVE-2021-2390
Published
Jul 20, 2021
Updated
Sep 26, 2024
Vendor
Oracle Corporation
Product
MySQL Server
Classifications
CWE-191, T1499.004, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 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=5.7.34 and prior
  2. Affected versionversion=8.0.25 and prior

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Oracle Corporation · MySQL Serverversion=5.7.34 and prior; version=8.0.25 and prior

Published CVSS scores

7.1NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:C
5.9OracleCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
9.8Zero Day InitiativeCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-191Integer Underflow (Wrap or Wraparound)
T1499.004Application or System Exploitation
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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