EUVD-2026-53457
GHSA-g2mx-jm98-x82v
Severity by source
AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
IOS XE processes unauthenticated network traffic; scope change reflects full device reload impacting all services; no confidentiality or integrity impact is supported by the description.
Primary rating from Vendor (cisco).
CVSS VectorVendor: cisco
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 software hardening releases that address multiple internally discovered vulnerabilities.
The vulnerabilities tracked by CVE-2026-20271 are related to insufficient control flow management issues that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-691.
AnalysisAI
Unauthenticated remote denial-of-service in Cisco IOS XE Software allows network-accessible attackers to crash IOS processes or force full device reloads by exploiting insufficient control flow management flaws (CWE-691), with a scope-changing availability impact rated CVSS 8.6. The vulnerabilities were discovered internally by Cisco's own engineering team as part of a proactive security review and addressed through software hardening releases - no active exploitation or public proof-of-concept has been identified at time of analysis. The affected version range is exceptionally broad, spanning IOS XE 16.6.x through 26.1.x, meaning virtually every Cisco IOS XE device on networks that has not been recently patched is likely running a vulnerable version.
Technical ContextAI
Cisco IOS XE is the Linux-kernel-based network operating system running on Cisco's enterprise routing and switching platforms, including Catalyst, ASR, ISR, CSR, and related families. The CPE string cpe:2.3:a:cisco:cisco_ios_xe_software:*:*:*:*:*:*:*:* confirms the vulnerability applies across all IOS XE platform sub-variants without exception. CWE-691 (Insufficient Control Flow Management) is a pillar-level weakness that encompasses improper exception handling, state machine logic errors, unreachable code, and malformed loop termination - root causes that in packet-processing or protocol-handling code paths can trigger IOS process crashes or full device reloads. Cisco's grouping of multiple distinct findings under a single CVE is consistent with their practice of consolidating related internally discovered defects into one advisory. The CVSS S:C scope-change metric indicates the availability impact extends beyond the initially faulting process, consistent with a device reload disrupting all routing, switching, and management services on the affected platform.
RemediationAI
The primary remediation is upgrading to a Cisco-released fixed version of IOS XE Software as specified in the Software Fixed Releases table within the Cisco Security Advisory at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxe-V8NMuMZJ - specific fixed version numbers are not present in the available intelligence data and must be confirmed directly from that advisory before planning upgrades. For organizations unable to immediately upgrade, the following compensating controls reduce exposure: deploy Control Plane Policing (CoPP) policies to rate-limit and filter unexpected or malformed traffic destined to the IOS XE control plane, reducing the attack surface for protocol-level triggering; apply Infrastructure Access-Lists (iACLs) to restrict which source addresses can reach management-plane and control-plane interfaces; and ensure management access (SSH, SNMP, NETCONF) is restricted to dedicated out-of-band management networks. These controls reduce but do not eliminate risk, particularly if the vulnerability is triggered by transit data-plane traffic rather than management-plane sessions - the exact trigger surface is not publicly documented, limiting the precision of protocol-specific workarounds.
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External POC / Exploit Code
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