CVE-2021-22976Network attack vector

Service degradation via WebSocket JSON parameter exhaustion

Published Feb 12, 2021 · Updated Aug 3, 2024

Resource exhaustion in F5 BIG-IP Advanced WAF and ASM allows remote attackers to degrade service with crafted WebSocket JSON requests. The ASM bd process consumes excessive CPU when it parses an unusually large number of parameters in the JSON payload. No authentication is required, but ASM must process the request; the reported consequence is CPU-driven service degradation rather than data access or modification.

CVSS severity7.5
High
EPSS probability1.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in F5 BIG-IP Advanced WAF and ASM allows remote attackers to degrade service with crafted WebSocket JSON requests. The ASM bd process consumes excessive CPU when it parses an unusually large number of parameters in the JSON payload. No authentication is required, but ASM must process the request; the reported consequence is CPU-driven service degradation rather than data access or modification.

The record

CVE
CVE-2021-22976
Published
Feb 12, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 12, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.003Application 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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