CVE-2021-23047Network attack vector

Service interruption via OCSP request memory growth

Published Sep 14, 2021 · Updated Aug 3, 2024

Uncontrolled resource consumption in F5 BIG-IP APM allows remote attackers to increase memory use during OCSP verification. The APM OCSP verifier processes undisclosed requests for certificates containing Authority Information Access data in a way that increases memory consumption; F5 has not disclosed the specific allocation error. The path requires APM to verify such a certificate, and the resulting memory pressure can degrade availability without affecting confidentiality or integrity.

CVSS severity5.3
Medium
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in F5 BIG-IP APM allows remote attackers to increase memory use during OCSP verification. The APM OCSP verifier processes undisclosed requests for certificates containing Authority Information Access data in a way that increases memory consumption; F5 has not disclosed the specific allocation error. The path requires APM to verify such a certificate, and the resulting memory pressure can degrade availability without affecting confidentiality or integrity.

The record

CVE
CVE-2021-23047
Published
Sep 14, 2021
Updated
Aug 3, 2024
Vendor
F5 Networks
Product
BIG-IP Access Policy Manager
Classifications
CWE-400, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=16.x before 16.1.0, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.3, and all versions of 13.1.x, 12.1.x and 11.6.x

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IP Access Policy Managerversion=16.x before 16.1.0, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.3, and all versions of 13.1.x, 12.1.x and 11.6.x

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.002Service Exhaustion Flood

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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