EUVD-2026-53456
GHSA-jmg2-f5xg-mf62
Severity by source
AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Network-reachable DoS with no auth or interaction needed; scope change reflects device-level crash disrupting all transit traffic beyond the process itself.
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 software hardening releases that address multiple internally discovered vulnerabilities.
The vulnerabilities tracked by CVE-2026-20270 are related to incorrect calculation issues that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-682.
AnalysisAI
Denial-of-service conditions in Cisco IOS XE Software stem from multiple incorrect calculation flaws (CWE-682) discoverable over the network without authentication, capable of crashing the affected device and disrupting all traffic transiting it. The CVSS scope change (S:C) indicates impact extends beyond the vulnerable component itself, consistent with a network appliance crash affecting downstream routing and switching functions across an enterprise. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Per the CVSS vector AV:N/AC:L/PR:N/UI:N, exploitation requires no authentication, no user interaction, and no special configuration - network-reachable Cisco IOS XE devices running affected versions are potentially vulnerable by default. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score of 8.6 (High) is driven by a favorable-to-attacker combination: network-reachable (AV:N), low complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), with a Changed Scope (S:C) and High availability impact (A:H). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An unauthenticated remote attacker sends specially crafted network traffic toward a Cisco IOS XE device, triggering one of the incorrect calculation flaws in a packet-processing or protocol-handling code path. The calculation error causes an affected IOS XE process to crash or forces an unexpected device reload, resulting in a complete loss of routing and switching functions for all traffic through that device until it recovers. … |
| Remediation | The primary remediation is to upgrade to a Cisco-released fixed version identified in the software hardening advisory at 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: contact Cisco TAC to confirm patch timeline for your affected IOS XE versions and request interim guidance; inventory all network devices running Cisco IOS XE by executing 'show version' on routers and switches to identify exposure. …
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External POC / Exploit Code
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