EUVD-2026-53459
GHSA-pc98-jj4f-x983
Severity by source
AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Network-reachable with no auth or interaction required; scope change reflects downstream network impact; availability-only impact confirmed by description and CVSS C:N/I:N.
Primary rating from Vendor (cisco).
CVSS VectorVendor: cisco
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Lifecycle Timeline
2DescriptionCVE.org
As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XE Software engineering team has conducted a comprehensive internal security review. This review resulted in a software hardening release that addresses multiple internally discovered vulnerabilities.
The vulnerabilities tracked by CVE-2026-20273 are related to improper input validation issues that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-20.
AnalysisAI
Unauthenticated remote denial-of-service affecting Cisco IOS XE Software across a wide version range results from multiple improper input validation flaws (CWE-20) discovered during Cisco's internal security hardening review. The CVSS vector (AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H) indicates that network-adjacent or internet-facing IOS XE devices can be crashed or rendered unavailable without any credentials or user interaction, with the changed scope (S:C) suggesting impact can extend beyond the directly targeted device to dependent network services. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | No special non-default configuration is required based on the CVSS vector (AV:N/AC:L/PR:N/UI:N), meaning any network-reachable Cisco IOS XE device in its default operating state is potentially vulnerable. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS base score of 8.6 with AV:N/AC:L/PR:N/UI:N places this in the highest-priority tier for network operators: no credentials, no special conditions, and low attack complexity mean any internet-reachable or intranet-accessible IOS XE management or data-plane interface is a viable attack surface. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An unauthenticated remote attacker sends a specially crafted network packet or malformed protocol message to a Cisco IOS XE device reachable over the network, triggering one of the improper input validation conditions. The affected IOS XE process crashes or enters an unresponsive state, causing the device to drop traffic or reload, disrupting network connectivity for all hosts dependent on that device. … |
| Remediation | The primary fix is to upgrade to a Cisco-recommended fixed release as specified in the Cisco Security Advisory cisco-sa-hardening-iosxe-V8NMuMZJ (https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxe-V8NMuMZJ). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, conduct a complete inventory of Cisco IOS XE devices deployed across your infrastructure and determine which software versions are currently installed, cross-referencing against Cisco's official list of affected versions for this vulnerability. …
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External POC / Exploit Code
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