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CVE-2026-39458: DoS in F5 BIG-IP DNS Cache
Plattform
linux
Komponente
bigip
Behoben in
21.0.0.1
CVE-2026-39458 describes a denial-of-service (DoS) vulnerability within F5 BIG-IP's DNS cache functionality. When a BIG-IP DNS profile with DNS cache enabled is configured on a virtual server, specially crafted traffic can trigger a crash in the Traffic Management Microkernel (TMM), resulting in service unavailability. This vulnerability impacts versions 16.1.0 through 21.0.0.1, and a fix is available in version 21.0.0.1.
Auswirkungen und Angriffsszenarienwird übersetzt…
The primary impact of CVE-2026-39458 is a denial-of-service condition. An attacker can exploit this vulnerability by sending malicious DNS requests to the affected BIG-IP system. Successful exploitation leads to TMM termination, which disrupts all traffic managed by that virtual server. This can result in significant downtime and impact critical applications and services relying on the BIG-IP infrastructure. The blast radius extends to any service or application dependent on the affected virtual server, potentially impacting a wide range of users and systems. While the vulnerability doesn't directly lead to data exfiltration or code execution, the service disruption can be a significant operational and business impact.
Ausnutzungskontextwird übersetzt…
CVE-2026-39458 is currently not listed on KEV (Known Exploited Vulnerabilities). The EPSS (Exploit Prediction Scoring System) score is pending evaluation. No public proof-of-concept (POC) code has been publicly released as of the publication date. CISA and F5 have published advisories regarding this vulnerability. Active exploitation campaigns are not currently confirmed, but the ease of sending DNS requests suggests a potential for opportunistic attacks.
Bedrohungsanalyse
Exploit-Status
CISA SSVC
CVSS-Vektor
Was bedeuten diese Metriken?
- Attack Vector
- Netzwerk — aus der Ferne über das Internet ausnutzbar. Kein physischer oder lokaler Zugriff erforderlich.
- Attack Complexity
- Niedrig — keine besonderen Bedingungen erforderlich. Zuverlässig ausnutzbar.
- Privileges Required
- Keine — ohne Authentifizierung ausnutzbar. Keine Zugangsdaten erforderlich.
- User Interaction
- Keine — automatischer und lautloser Angriff. Das Opfer tut nichts.
- Scope
- Unverändert — Auswirkung auf das anfällige Komponente beschränkt.
- Confidentiality
- Keine — kein Vertraulichkeitseinfluss.
- Integrity
- Keine — kein Integritätseinfluss.
- Availability
- Hoch — vollständiger Absturz oder Ressourcenerschöpfung. Totaler Denial of Service.
Betroffene Software
Schwachstellen-Klassifikation (CWE)
Zeitleiste
- Reserviert
- Veröffentlicht
Mitigation und Workaroundswird übersetzt…
The recommended mitigation for CVE-2026-39458 is to upgrade to BIG-IP version 21.0.0.1 or later, which contains the fix. If immediate upgrade is not feasible, consider implementing temporary workarounds. One potential workaround involves rate-limiting DNS requests at the virtual server level to reduce the impact of malicious traffic. Additionally, deploying a Web Application Firewall (WAF) or reverse proxy in front of the BIG-IP can help filter out malicious DNS requests. Monitor BIG-IP system logs for unusual DNS activity and consider implementing intrusion detection signatures to identify potential exploitation attempts. After upgrading, confirm the fix by sending a series of crafted DNS requests to the system and verifying that TMM remains stable.
So behebenwird übersetzt…
Actualice su sistema BIG-IP a una versión corregida. Consulte la nota de seguridad de F5 (https://my.f5.com/manage/s/article/K000160945) para obtener información detallada sobre las versiones corregidas y los pasos de mitigación.
Häufig gestellte Fragenwird übersetzt…
What is CVE-2026-39458 — DoS in F5 BIG-IP DNS Cache?
CVE-2026-39458 is a denial-of-service vulnerability in F5 BIG-IP's DNS cache. Malformed DNS traffic can crash the Traffic Management Microkernel (TMM), causing service disruption. It affects versions 16.1.0–21.0.0.1.
Am I affected by CVE-2026-39458 in F5 BIG-IP?
You are affected if you are running F5 BIG-IP versions 16.1.0 through 21.0.0.1 with a DNS profile enabled and DNS cache configured on a virtual server.
How do I fix CVE-2026-39458 in F5 BIG-IP?
Upgrade to F5 BIG-IP version 21.0.0.1 or later to resolve the vulnerability. If immediate upgrade isn't possible, consider rate-limiting DNS requests or deploying a WAF.
Is CVE-2026-39458 being actively exploited?
Active exploitation campaigns are not currently confirmed, but the vulnerability's nature suggests a potential for opportunistic attacks. Monitor your systems closely.
Where can I find the official F5 advisory for CVE-2026-39458?
Refer to the official F5 Security Advisory: [https://www.f5.com/service/security-advisories/advisory/f5-security-advisory-39458](https://www.f5.com/service/security-advisories/advisory/f5-security-advisory-39458)
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