What is the CVSS score of EUVD-2026-53459?

EUVD-2026-53459 has a CVSS 3.1 base score of 8.6 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H. EPSS exploitation probability: 0.3%.

Which versions of Cisco IOS XE are affected by EUVD-2026-53459?

Cisco IOS XE devices are vulnerable to unauthenticated remote denial-of-service attacks that can crash network infrastructure and disrupt business operations across the organization.

How to fix or mitigate EUVD-2026-53459?

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. Within 7 days, implement network segmentation and access controls by deploying firewall rules and network access control lists to restrict unauthenticated network access to all IOS XE devices, enable enhanced syslog and NetFlow monitoring on affected devices to detect anomalous activity and crash events, and subscribe to Cisco's security advisory service to track patch availability. Within 30 days, establish a routine monitoring process for Cisco security updates; upon patch availability, create a comprehensive testing and deployment plan validated in a non-production environment before production rollout; if patches are delayed or unavailable, escalate risk findings to executive management and formally document all compensating controls in your risk management system.

Cisco IOS XE EUVD-2026-53459

| CVE-2026-20273 HIGH

Improper Input Validation (CWE-20)

2026-08-05 cisco

GHSA-pc98-jj4f-x983

Information Disclosure Apple Cisco Cisco Ios Xe Software

8.6

CVSS 3.1 · Vendor: cisco

Severity by source

Vendor (cisco) PRIMARY

8.6 HIGH

AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

vuln.today AI

8.6 HIGH

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.

3.1 AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

Primary rating from Vendor (cisco).

CVSS VectorVendor: cisco

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Aug 05, 2026 - 17:26 vuln.today

CVE Published

Aug 05, 2026 - 16:19 nvd

HIGH 8.6

DescriptionCVE.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. No public exploit code has been identified and this is not listed in CISA KEV, consistent with the internally discovered origin.

Technical ContextAI

Cisco IOS XE Software is the operating system running on Cisco's enterprise routing and switching hardware. The root cause class is CWE-20 (Improper Input Validation), the parent pillar CWE covering failures to validate, filter, or sanitize input before use. The CVE description explicitly notes that multiple distinct validation issues are grouped under this single CVE identifier as part of a coordinated hardening release, meaning the attack surface spans more than one input-processing pathway within IOS XE. The CPE string cpe:2.3:a:cisco:cisco_ios_xe_software:*:*:*:*:*:*:*:* confirms all editions of IOS XE software are in scope. The CVSS scope change (S:C) is consistent with how IOS XE failures propagate: a crashed control-plane process on a core router or switch can disrupt traffic for an entire network segment, extending the availability impact beyond the single device.

RemediationAI

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). Specific fixed release version numbers were not included in the data available at time of analysis - consult the advisory directly to identify the appropriate target release for your software train, as Cisco typically publishes a fixed-release table mapping each affected train to its remediated version. Where immediate upgrade is not feasible, restrict management-plane and data-plane access to IOS XE devices using infrastructure ACLs (iACLs) to limit which sources can send traffic to the device, reducing exposure for the specific input pathways involved. Control-plane policing (CoPP) policies can be tuned to rate-limit or drop unexpected protocol traffic targeting the device, though this does not eliminate the vulnerability and may affect legitimate traffic. These compensating controls are interim measures only; vendor-patching remains the authoritative remediation.