CVE-2026-39458Network attack vector

TMM termination via uninitialized pointer access

Published May 13, 2026 · Updated May 13, 2026

Access of an uninitialized pointer in F5 BIG-IP allows remote attackers to terminate TMM through traffic to a DNS-caching virtual server. F5 identifies the pointer error but has not disclosed the parsing path or traffic characteristic that leaves the pointer uninitialized. The issue is reachable without credentials only when a BIG-IP DNS profile with DNS cache is configured on a virtual server, and its reported consequence is traffic-processing interruption rather than data disclosure or modification.

CVSS severity8.7
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access of an uninitialized pointer in F5 BIG-IP allows remote attackers to terminate TMM through traffic to a DNS-caching virtual server. F5 identifies the pointer error but has not disclosed the parsing path or traffic characteristic that leaves the pointer uninitialized. The issue is reachable without credentials only when a BIG-IP DNS profile with DNS cache is configured on a virtual server, and its reported consequence is traffic-processing interruption rather than data disclosure or modification.

The record

CVE
CVE-2026-39458
Published
May 13, 2026
Updated
May 13, 2026
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-824, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record 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=16.1.0 <*
  2. Affected versionversion=17.1.0 <17.1.3.2
  3. Affected versionversion=17.5.0 <17.5.1.6
  4. Affected versionversion=21.0.0 <21.0.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=16.1.0 <*; version=17.1.0 <17.1.3.2; version=17.5.0 <17.5.1.6; version=21.0.0 <21.0.0.1

Published CVSS scores

7.5F5 NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7F5 NetworksCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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-824Access of Uninitialized Pointer
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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