What is the CVSS score of EUVD-2026-53454?

EUVD-2026-53454 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-2026-53454?

Cisco IOS XE Software (versions 16.6.x through 26.1.x) is vulnerable to remote unauthenticated denial-of-service attacks (CVSS 8.6) that can disable routing and switching infrastructure, with…

How to fix or mitigate EUVD-2026-53454?

Within 24 hours, inventory all Cisco IOS XE devices and identify which are running versions 16.6.x through 26.1.x, then assess the business criticality of each affected device. Within 7 days, review Cisco's published security advisory for configuration hardening or workaround options, implement network access controls to restrict remote connectivity to affected devices where operationally feasible, and deploy network monitoring signatures for exploitation attempts. Within 30 days, establish a rapid-deployment process for Cisco security updates and apply any released patches for CVE-2026-20268 to all affected devices, prioritizing critical production infrastructure and internet-facing network equipment.

Cisco IOS XE EUVD-2026-53454

| CVE-2026-20268 HIGH

Buffer Overflow (CWE-119)

2026-08-05 cisco

GHSA-3vcg-p7rg-2799

Buffer Overflow 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-exploitable unauthenticated memory corruption causes high availability impact with scope change due to IOS XE's critical routing/switching role; no confidentiality or integrity impact identified.

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 - 17:29 vuln.today

CVE Published

Aug 05, 2026 - 16:18 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 software hardening releases that address multiple internally discovered vulnerabilities.

The vulnerabilities tracked by CVE-2026-20268 are related to issues with improper restriction of operations within the bounds of a memory buffer that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-119.

AnalysisAI

Remote unauthenticated exploitation of improper memory buffer boundary handling in Cisco IOS XE Software can cause a complete denial of service with Changed scope (S:C), potentially cascading disruption to downstream network segments that depend on the affected routing or switching infrastructure. Affecting an extremely broad range of IOS XE release trains from 16.6.x through 26.1.x across hundreds of specific builds, this vulnerability was discovered and self-reported by Cisco's own engineering team during a proactive internal security hardening review - not in response to observed attacks. No public exploit code or CISA KEV listing has been identified at time of analysis, which moderates near-term opportunistic exploitation risk despite the high CVSS score of 8.6.

Technical ContextAI

CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) is a pillar-level weakness encompassing buffer overflows, heap overflows, out-of-bounds reads, and related memory safety violations common in C/C++ network software. Cisco IOS XE is a Linux-based network operating system running on Cisco Catalyst switches, ISR/ASR/CSR routers, and other enterprise-class network appliances - the software layer identified by CPE cpe:2.3:a:cisco:cisco_ios_xe_software:*:*:*:*:*:*:*:*. The network attack vector (AV:N) and no-authentication (PR:N) CVSS metrics are consistent with a vulnerability triggered via a network-facing protocol handler or packet-parsing code path rather than a locally-accessible management interface. The Changed scope (S:C) in the CVSS vector reflects that exploitation of the IOS XE process boundary produces impact beyond the directly targeted process - consistent with the critical routing and switching role these devices play across enterprise and service-provider networks. The specific protocol, service, or feature within IOS XE that triggers the unsafe memory operation is not disclosed in the available advisory data.

RemediationAI

Consult the Cisco Security Advisory cisco-sa-hardening-iosxe-V8NMuMZJ (https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxe-V8NMuMZJ) and use Cisco's Software Checker tool to identify the specific fixed IOS XE release for your platform and train - exact patched version numbers per train are not enumerated in available intelligence data and must be confirmed directly via the advisory. If immediate upgrade cannot be performed, reduce exposure by implementing infrastructure access control lists (iACLs) that restrict which source IP addresses can send traffic to the device's control and management plane interfaces, limiting the network-reachable attack surface. Control Plane Policing (CoPP) policies can additionally rate-limit or drop unexpected protocol traffic before it reaches vulnerable processing components - this reduces risk but does not eliminate it. Disabling any unused network services or protocols on device interfaces may further shrink attack surface if the vulnerable code path is tied to a specific feature, though the specific triggering feature is not disclosed. Patching to a Cisco-provided fixed release remains the definitive and only fully effective remediation.