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Full vulnerability report · 2026
CVE-2026-39458High confidence

BIG-IP DNS Cache vulnerability

F5 · BIG-IP

8.7HighCVSS 4.0
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-29967

No EUVD known-exploited evidence

When a BIG-IP is configured with DNS caching (Such as a DNS profile with caching enabled, SSL Orchestrator, Advanced WAF DoS protection), undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
8.7 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

When a BIG-IP is configured with DNS caching (Such as a DNS profile with caching enabled, SSL Orchestrator, Advanced WAF DoS protection), undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

What

When a BIG-IP is configured with DNS caching (Such as a DNS profile with caching enabled, SSL Orchestrator, Advanced WAF DoS protection), undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Why

The product accesses or uses a pointer that has not been initialized.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

When a BIG-IP is configured with DNS caching (Such as a DNS profile with caching enabled, SSL Orchestrator, Advanced WAF DoS protection), undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Why

The product accesses or uses a pointer that has not been initialized.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Access of Uninitialized Pointer → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-824 ↗

CWE-824: Access of Uninitialized Pointer. The product accesses or uses a pointer that has not been initialized.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-824
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-29967Official EUVD mapping

When a BIG-IP is configured with DNS caching (Such as a DNS profile with caching enabled, SSL Orchestrator, Advanced WAF DoS protection), undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Official EUVD record
BSI · German · WID-SEC-W-2026-1532F5 BIG-IP Produkte: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in F5 BIG-IP ausnutzen, um beliebigen Programmcode auszuführen, erweiterte Berechtigungen zu erlangen, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren oder offenzulegen oder einen Denial-of-Service-Zustand zu verursachen.

Official advisory
CERT-FR · French · CERTFR-2026-AVI-0591Multiples vulnérabilités dans les produits F5

d?id=CVE-2026-20916 Référence CVE CVE-2026-24464 https://www.cve.org/CVERecord?id=CVE-2026-24464 Référence CVE CVE-2026-28758 https://www.cve.org/CVERecord?id=CVE-2026-28758 Référence CVE CVE-2026-32643 https://www.cve.org/CVERecord?id=CVE-2026-32643 Référence CVE CVE-2026-32673 https://www.cve.org/CVERecord?id=CVE-2026-32673 Référence CVE CVE-2026-34019 https://www.cve.org/CVERecord?id=CVE-2026-34019 Référence CVE CVE-2026-34176 https://www.cve.org/CVERecord?id=CVE-2026-34176 Référence CVE CVE-2026-35062 https://www.cve.org/CVERecord?id=CVE-2026-35062 Référence CVE CVE-2026-39455 https://www.cve.org/CVERecord?id=CVE-2026-39455 Référence CVE CVE-2026-39458 https://www.cve.org/CVERecord?id=CVE-2026-39458 Référence CVE CVE-2026-39459 https://www.cve.org/CVERecord?id=CVE-2026-39459 Référence CVE CVE-2026-40060 https://www.cve.org/CVERecord?id=CVE-2026-40060 Référence CVE CVE-2026-40061 https://www.cve.org/CVERecord?id=CVE-2026-40061 Référence CVE CVE-2026-40067 https://www.cve.org/CVERecord?id=CVE-2026-40067 Référence CVE CVE-2026-40423 https://www.cve.org/CVERecord?id=CVE-2026-40423 Référence CVE CVE-2026-40435 https://www.cve.org/CVERecord?id=CVE-2026-40435 Référence CVE CVE-2026-40460 https://www.cve.org/CVERecord?id=CVE-2026-40460 Référence CVE CVE-2026-40462 https://www.cve.org/CVERecord?id=

Official advisory
NCSC-NL · Dutch · NCSC-2026-0162Kwetsbaarheden verholpen in F5 BIG-IP en BIG-IQ producten

Enabling a BIG-IP DNS profile with DNS cache on a virtual server can cause the Traffic Management Microkernel (TMM) to terminate due to undisclosed traffic, with unsupported software versions not evaluated.

Official advisory
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
21.0.0 < 21.0.0.1; 17.5.0 < 17.5.1.6; 17.1.0 < 17.1.3.2; 16.1.0 < *
Fixed
21.1.0 < *
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04

Evidence and provenance

Published 13 May 2026 · Last source change 24 Aug 2026, 21:39 UTC · CWE-824 · Access of Uninitialized Pointer

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-29967
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates →

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-29967↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-39458 · cve.blacktree.nl