Cyber Resilience

CVE-2026-20301

Published
05 August 2026
Modified
06 August 2026
CVSS Score v3.1 8.6
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
EPSS Score 0.0033 25th percentile
Risk Priority 61 floored blend · peak EPSS

Summary

CVE-2026-20301 is a high-severity Unchecked Input for Loop Condition (CWE-606) vulnerability in Cisco IOS Software (inferred from references). Its CVSS base score is 8.6 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 25th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

A vulnerability in the Extensible Messaging Client Protocol (XMCP), also referred to as the External Client protocol, of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition…

more

on an affected device. This vulnerability is due to improper handling of malformed XMCP packets. An attacker could exploit this vulnerability by sending a malformed XMCP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload unexpectedly, resulting in a DoS condition. The attacker does not need the XMCP client username to exploit this vulnerability.

CWE(s)
CWE-606

Related Threats

MITRE ATT&CK Enterprise Techniques

T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-43801Shared CWE-606
CVE-2026-27689Shared CWE-606
CVE-2023-6237Shared CWE-606
CVE-2025-42930Shared CWE-606
CVE-2024-13930Shared CWE-606
CVE-2026-41986Shared CWE-606
CVE-2024-13931Shared CWE-606
CVE-2026-62901Shared CWE-606
CVE-2026-0243Shared CWE-606
CVE-2024-34486Shared CWE-606

Affected Assets

Cisco
IOS Software
inferred from references and description; NVD did not file a CPE for this CVE

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

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Validate
Prove the fix (OWASP ASVS)
  • V17.3.2
  • V4.3.1

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

Input validation directly stops untrusted values from reaching loop conditions without bounds or sanity checks.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input validation and bounds checking that prevent unchecked loop conditions.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development can detect and block unchecked loop conditions before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle requires input validation and bounds checking that can prevent unchecked loop conditions.

A.8.26 Application security requirements partial match
prevents

Application security requirements include input validation rules that mitigate excessive looping from untrusted data.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly mandate validation of loop-control inputs to prevent unbounded iteration.

References