[NEW] [high] Cisco IOS: Vulnerability Enables Denial of Service

highCVE-2026-20301

A remote, anonymous attacker can exploit a vulnerability in Cisco IOS and Cisco IOS XE to conduct a denial of service attack.

CSIRTS triage

vendor: Cisco product: IOS Denial of service

What: A vulnerability in Cisco IOS and Cisco IOS XE allows remote anonymous attackers to conduct denial of service attacks.
Who is affected: Devices running vulnerable Cisco IOS and IOS XE versions.
Urgency: High severity denial of service in widely-deployed network infrastructure requires prompt patching.
Action: Check Cisco security advisories for affected IOS versions and apply patches.

AI-assisted analysis generated from the source advisory — verify against the original.

⚡ Watch IOS

Get an email when a new IOS advisory drops — max one per day, one-click unsubscribe.

Details

Source: CERT-Bund (BSI) Security Advisories (DE · national-cert · site)
Severity: high
Published: 2026-08-06
Exploitation: Not in CISA KEV at last sync
Language: Machine-translated to English — verify against the original

Original advisory: https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-2664

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-203010.33% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 25% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-20301	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

unknownCisco Products Multiple Vulnerabilitieshkcert
unknownMultiple vulnerabilities in Cisco products (August 6, 2026)cert-fr-avis
highCVE-2026-20301: A vulnerability in the Extensible Messaging Client Protocol (XMCP), also referred to as the Ex…nvd
criticalCisco Advance Notification for Publication of August 5, 2026, Security Advisoriescisco-psirt
highCisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Service Vulnerabilitycisco-psirt

Recent advisories for Cisco IOS

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

high[NEW] [high] Cisco IOS XE: Multiple Vulnerabilitiescert-bund · 2026-08-06
mediumCVE-2026-20311: A vulnerability in the web-based management interface of Cisco IOS XE Software could allow an …nvd · 2026-08-05
mediumCVE-2026-20308: A vulnerability in the web-based management interface of Cisco IOS XE Software could allow an …nvd · 2026-08-05
highCVE-2026-20301: A vulnerability in the Extensible Messaging Client Protocol (XMCP), also referred to as the Ex…nvd · 2026-08-05
highCVE-2026-20273: As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS…nvd · 2026-08-05
criticalCVE-2026-20272: As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS…nvd · 2026-08-05