Cyber Resilience

CVE-2026-20074

Cisco Ios Xr 7.8.0 – 25.2.2

Published
11 March 2026
Modified
08 July 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.4
Click a component to see what it means
Raw vectorCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
EPSS Score 0.0016 6th percentile
Risk Priority 52 floored blend · peak EPSS

Summary

CVE-2026-20074 is a high-severity Improper Validation of Specified Type of Input (CWE-1287) vulnerability in Cisco Ios Xr. Its CVSS base score is 7.4 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 6th 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.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-20074 is a vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software. It stems from insufficient input validation of ingress IS-IS packets, which could allow an unauthenticated, adjacent attacker to cause the IS-IS process to restart unexpectedly. The vulnerability affects devices running this software where the IS-IS protocol is enabled, and it has a CVSS v3.1 base score of 7.4 (AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H), associated with CWE-1287.

An attacker must be Layer 2-adjacent to the affected device and form an IS-IS adjacency before exploiting the issue by sending crafted IS-IS packets. A successful exploit would restart the IS-IS process, leading to a temporary loss of connectivity to advertised networks and resulting in a denial-of-service (DoS) condition on the device.

Cisco has published a security advisory detailing the vulnerability, affected releases, and mitigation options, available at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK.

EU & UK References

Vulnerability Data

A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the IS-IS process to restart unexpectedly. This vulnerability is due to insufficient input validation of ingress…

more

IS-IS packets. An attacker could exploit this vulnerability by sending crafted IS-IS packets to an affected device after forming an adjacency. A successful exploit could allow the attacker to cause the IS-IS process to restart unexpectedly, resulting in a temporary loss of connectivity to advertised networks and a denial of service (DoS) condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device and must have formed an adjacency.  

CWE(s)
CWE-1287

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-20115Same product: Cisco Ios Xr
CVE-2009-2055Same product: Cisco Ios Xr
CVE-2024-20406Same product: Cisco Ios Xr
CVE-2023-20190Same product: Cisco Ios Xr
CVE-2024-20483Same product: Cisco Ios Xr
CVE-2024-20398Same product: Cisco Ios Xr
CVE-2025-20138Same product: Cisco Ios Xr
CVE-2024-20319Same product: Cisco Ios Xr
CVE-2023-20191Same product: Cisco Ios Xr
CVE-2024-20408Same vendor: Cisco

Affected Assets

cisco
ios xr
25.3.0 · 7.8.0 — 25.2.2

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.1.1
  • V1.4.2
  • V2.1.1
  • V2.2.2

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

SI-10 directly requires validation of information inputs, which structurally prevents type-validation failures from being introduced or exploitable.

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 proper input type validation during development.

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 can detect type-validation flaws but does not prevent them during development.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and type checking to prevent improper type handling.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly include validation of input data types and formats.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles promote defensive input handling and type enforcement at system boundaries.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly require proper type validation of all external inputs.

References