Cisco IOS, IOS XE, Secure Firewall Threat Defense Denial of Service Vulnerability

CERT-Bund Security Advisories

Published March 25th, 2026

Detected March 26th, 2026

Summary

CERT-Bund has issued a security advisory regarding a Denial of Service vulnerability affecting Cisco IOS, Cisco IOS XE, and Cisco Secure Firewall Threat Defense. The vulnerability has a CVSS Base Score of 8.6 and can be exploited remotely.

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What changed

CERT-Bund has published advisory WID-SEC-2026-0866 detailing a critical Denial of Service (DoS) vulnerability affecting Cisco IOS, Cisco IOS XE, and Cisco Secure Firewall Threat Defense. The vulnerability, with a CVSS Base Score of 8.6, allows remote, anonymous attackers to disrupt services. The advisory indicates that mitigation measures are available.

Organizations utilizing affected Cisco products should immediately review the advisory and implement available mitigation strategies to prevent potential service disruptions. While no specific compliance deadline is stated, prompt action is recommended to address the high-severity vulnerability and protect network availability. Failure to mitigate could lead to significant operational impact due to DoS attacks.

What to do next

Review CERT-Bund advisory WID-SEC-2026-0866 for details on the Cisco IOS, IOS XE, and Secure Firewall Threat Defense vulnerability.
Implement available mitigation measures as recommended by Cisco and CERT-Bund.
Assess the impact of the vulnerability on your network infrastructure and services.

Source document (simplified)

[WID-SEC-2026-0866] Cisco IOS, Cisco IOS XE und Cisco Secure Firewall Threat Defense: Schwachstelle ermöglicht Denial of Service CVSS Base Score 8.6 (hoch) CVSS Temporal Score 7.5 (hoch) Remoteangriff ja Datum 25.03.2026 Stand 26.03.2026 Mitigation ja

Betroffene Systeme

Betriebssystem

Sonstiges

Produktbeschreibung

Cisco Internetwork Operating System (IOS) ist ein Betriebssystem, das für Cisco Geräte wie z. B. Router und Switches eingesetzt wird.
Cisco Secure Firewall Threat Defense ist eine Sicherheitslösung, die Funktionen wie Firewall, Intrusion Prevention und erweiterten Malware-Schutz in einer einzigen Appliance integriert.

Produkte

25.03.2026
- Cisco IOS

Cisco IOS XE
Cisco Secure Firewall Threat Defense

Angriff

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in Cisco IOS, Cisco IOS XE und Cisco Secure Firewall Threat Defense ausnutzen, um einen Denial of Service Angriff durchzuführen. CVE Informationen Versionshistorie Feedback zum Advisory geben