Cyber Resilience

CVE-2026-20274

Cisco Ios Xr 24.1.1 … 7.9.21

Published
02 September 2026
Modified
17 September 2026
Patch / advisory
View advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0073 53th percentile
Risk Priority 72 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-20274 is a critical-severity Improper Control of a Resource Through its Lifetime (CWE-664) vulnerability in Cisco Ios Xr. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Access Token Manipulation (T1134); ranked in the top 47% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SC-39 (Process Isolation) and SC-4 (Information in Shared System Resources) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XR Software engineering team has conducted a comprehensive internal security review. This review resulted in a software hardening releases that address multiple internally discovered vulnerabilities.…

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The vulnerabilities tracked by CVE-2026-20274 are related to improper resource control issues that are grouped under the Common Weakness Enumeration (CWE) CWE-664.

CWE(s)
CWE-664

Related Threats

MITRE ATT&CK Enterprise Techniques

T1134 Access Token Manipulation Stealth
Adversaries may modify access tokens to operate under a different user or system security context to perform actions and bypass access controls.
attack.mitre.org →
T1134.002 Create Process with Token Stealth
Adversaries may create a new process with an existing token to escalate privileges and bypass access controls.
attack.mitre.org →
T1606 Forge Web Credentials Credential Access
Adversaries may forge credential materials that can be used to gain access to web applications or Internet services.
attack.mitre.org →
T1055 Process Injection Stealth
Adversaries may inject code into processes in order to evade process-based defenses as well as possibly elevate privileges.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1134.001 Token Impersonation/Theft Stealth
Adversaries may duplicate then impersonate another user's existing token to escalate privileges and bypass access controls.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-43503Shared CWE-664
CVE-2024-7889Shared CWE-664
CVE-2024-41169Shared CWE-664
CVE-2026-20158Shared CWE-664
CVE-2025-21593Shared CWE-664
CVE-2023-44288Shared CWE-664
CVE-2023-25942Shared CWE-664
CVE-2022-27518Shared CWE-664
CVE-2023-52387Shared CWE-664
CVE-2023-44295Shared CWE-664

Affected Assets

cisco
ios xr
24.1.1, 24.1.2, 24.2.1, 24.2.11, 24.2.2

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 4 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)

—

Mitigating Controls (NIST 800-53 r5) AI

SC-39 Process Isolation partial match

SC-39 enforces separate execution domains so one process cannot corrupt or misuse another process's resources across their lifetimes.

SC-4 Information in Shared System Resources partial match

SC-4 prevents unintended information transfer through shared resources, limiting blast radius when a product fails to release or reuse resources correctly.

SI-16 Memory Protection partial match

SI-16 blocks unauthorized code execution in memory, stopping exploitation that commonly follows improper allocation, use-after-free, or deallocation errors.

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.

ID.AM-08 partial match
prevents

Directly requires managing assets through creation, use, and disposal phases, preventing lifetime control failures.

PR.PS-01 partial match
prevents

Enforces consistent configuration and handling rules that reduce improper resource lifetime management.

PR.PS-02 partial match
prevents

Covers ongoing maintenance and removal of software, indirectly limiting resource lifetime issues.

PR.PS-03 partial match
prevents

Addresses hardware maintenance and replacement phases that intersect with resource lifetime control.

PR.PS-06 partial match
prevents

Integrates secure practices across the full development lifecycle, addressing resource creation-to-release control.

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.8.10 Information deletion partial match
prevents

Information deletion control ensures proper release and sanitization at end of life.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC embeds resource lifecycle controls from design through decommissioning.

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

Secure architecture principles reduce lifetime control issues but are not specific to them.

A.8.28 Secure coding partial match
prevents

Secure coding practices help avoid lifetime control bugs but do not address the full scope.

A.8.9 Configuration management partial match
degrades

Configuration management enforces lifecycle rules for resource creation, use and disposal.

A.8.32 Change management none match
mitigates

Change management governs resource modifications but does not cover creation or release.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).

Windows Server 2016 (2 rules)
  • V-224971 The Active Directory SYSVOL directory must have the proper access control permissions. prevents CWE-664
  • V-224970 Permissions on the Active Directory data files must only allow System and Administrators access. prevents CWE-664
Windows Server 2019 (1 rule)
  • V-205739 Windows Server 2019 permissions on the Active Directory data files must only allow System and Administrators access. prevents CWE-664

References