CVE-2020-5856Network attack vector

Service interruption via crafted xnet traffic

Published Feb 6, 2020 · Updated Aug 4, 2024

Denial of service in F5 BIG-IP 14.1.0 through 14.1.2.2 and 15.0.0 through 15.0.1.1 allows remote attackers to restart TMM. The default xnet driver mishandles specifically crafted traffic during TCP packet transmission, but F5 has not disclosed the faulty operation. Exploitation requires an AWS-hosted Virtual Edition instance using xnet; successful traffic delivery interrupts application traffic while TMM restarts.

CVSS severity7.5
High
EPSS probability1.04%
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 F5 BIG-IP 14.1.0 through 14.1.2.2 and 15.0.0 through 15.0.1.1 allows remote attackers to restart TMM. The default xnet driver mishandles specifically crafted traffic during TCP packet transmission, but F5 has not disclosed the faulty operation. Exploitation requires an AWS-hosted Virtual Edition instance using xnet; successful traffic delivery interrupts application traffic while TMM restarts.

The record

CVE
CVE-2020-5856
Published
Feb 6, 2020
Updated
Aug 4, 2024
Vendor
F5 Networks
Product
BIG-IP
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 6, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=14.1.0-14.1.2.2
  2. Affected versionversion=15.0.0-15.0.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=14.1.0-14.1.2.2; version=15.0.0-15.0.1.1

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NVDAV: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

T1499.004Application or System Exploitation

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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