CVE-2020-5871Network attack vector

Unauthenticated service interruption via HTTP/2 cipher handling

Published Apr 30, 2020 · Updated Aug 4, 2024

Denial of service in F5 Networks BIG-IP 14.1.0 through 14.1.2.3 allows remote attackers to interrupt HTTP/2 virtual servers. F5 identifies TMM as the locus but does not disclose how it mishandles the triggering requests; the condition involves RFC-blacklisted ciphers on backend servers. Reachability requires an HTTP/2 virtual server with that backend-cipher condition, and the resulting interruption affects the data plane rather than the control plane.

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 Networks BIG-IP 14.1.0 through 14.1.2.3 allows remote attackers to interrupt HTTP/2 virtual servers. F5 identifies TMM as the locus but does not disclose how it mishandles the triggering requests; the condition involves RFC-blacklisted ciphers on backend servers. Reachability requires an HTTP/2 virtual server with that backend-cipher condition, and the resulting interruption affects the data plane rather than the control plane.

The record

CVE
CVE-2020-5871
Published
Apr 30, 2020
Updated
Aug 4, 2024
Vendor
F5 Networks
Product
BIG-IP
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 30, 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=14.1.0-14.1.2.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=14.1.0-14.1.2.3

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.

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 Denial of Service

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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